In 1999, it was reported that 57,000 patients in the United States sustain a midshaft femoral fractures, annually.1 The majority of these injuries occur in young, otherwise healthy, individuals and are the result of significant, high-energy trauma, such as motor vehicle accidents, falls from a height, or industrial accidents.2 Due to the traumatic high-energy nature of this injury and the current surgical intervention, resultant soft tissue pathology is common. Soft tissue injuries intrinsic to the fracture and iatrogenic muscle injury associated with the surgical intervention create additional impairments and ultimately may limit return to the previous level of function.3-9
Current evidence suggests that a significant cohort of femur fracture patients managed with an intramedullary (IM) nail will ultimately possess residual impairments and disability up to 3 years after surgery.2,3,10 It has been reported that approximately one half of patients treated for a leg fracture at level I trauma centers have some residual disability 12 months after the injury, and up to 20% of individuals treated surgically for femoral shaft fractures are unable to return to work 3 years after the injury.9,11 In a multicenter study of severe lower extremity injuries, approximately 70% of patients were able to return to work 12 months post injury; however, the chances of returning to work markedly decline after that time.12 This evidence validates the need to aggressively manage these patients in an attempt to progress them back to their prior level of function quickly, to avoid the risk of permanent disability. Further investigation of functional outcomes and rehabilitation are required to minimize disability after surgical fixation of femoral shaft fractures.
Surgical treatment of femoral shaft fractures with an IM nail is considered the standard of care with union rates between 95% and 99%,13 Despite this success, functional limitations and impairments often persist after the injury and surgical procedure, which may result in residual disability.2,3,13 This disconnect between fracture union and residual functional impairments suggests that factors other than fracture healing may contribute to the long-term outcome in femur fracture patients. As previously suggested, these residual functional limitations, impairments, and ultimate disabilities may be due to soft tissue injury and compromise as a result of trauma at the time of either injury and/or surgery.3 The most common soft tissue limitations and impairments identified in the literature include hip abduction weakness with a resultant Trendelenburg gait pattern, quadriceps weakness, anterior knee pain, and decreased function with respect to gait and walking endurance.2,4-8
FUNCTIONAL IMPAIRMENTS AFTER FEMORAL SHAFT FRACTURE
Hip Abductor Function
Hip abduction weakness is described as a common complication of femoral IM nailing.2,4,5,14,15 Several authors have demonstrated side-to-side deficits in hip abduction strength with resultant alterations in gait, specifically a Trendelenburg gait pattern at time points up to 47 months after surgery.2,4 In addition, hip abduction weakness in this population has been identified as a complication, which ultimately leads to additional functional limitations, including stiffness, antalgic gait, decreased endurance with stairs, and difficulty ambulating stairs.2,4,5,14,16 The mechanism suggested by these authors was attributed to soft tissue injury at the time of either injury or surgery, an irritation of the abductor musculature from the surgical hardware, or inadequate postoperative rehabilitation.2 Inadequate postoperative rehabilitation, although frequently identified as a potential cause of this impairment, has not been documented adequately in the literature, nor prospectively analyzed. Bain et al2 studied femur fracture patients treated with an antegrade IM nail and compared hip abduction strength to a control group. Their objective was to compare hip abduction function and strength after insertion of a femoral IM nail. They enrolled 32 patients with IM nailing after femoral shaft fracture, 14 patients with IM nailing after closed femoral shortening, and 40 controls. At a mean follow-up of 47 ± 13 (minimum = 24) months, the patients demonstrated 14% deficit in mean hip abduction strength. In addition, a positive correlation was found between hip abduction weakness and several functional complaints, including pain, stiffness, antalgic gait, decreased endurance with stairs, and difficulty ambulating stairs. Residual weakness was attributed to soft tissue injury at the time of either injury or surgery, an irritation of the abductor musculature from the surgical hardware or inadequate postoperative rehabilitation. Ostrum et al5 studied 14 patients with an antegrade femoral IM nail after an isolated femur fracture. They did not report strength measures; however, they did report that 2 patients had persistent Trendelenburg gait due to hip weakness despite radiographic evidence of bony healing. The rehabilitation used and control data were not reported in this study. Other authors4,5,17,18 have also identified hip abduction weakness as a complication after antegrade IM nailing, which may lead to functional limitations. Inadequate postoperative rehabilitation is a potential cause of delayed strength. Although several studies cite inadequate rehabilitation as a contributing factor to this impairment, few have described rehabilitations program or prospectively analyzed this variable.
Quadriceps Femoris Function
Impaired quadriceps strength has also been identified as a common outcome after femoral fracture with or without surgical management.3,6,7,19 Numerous authors have documented that after both conservative and operative6,7,19 management of femoral fractures, significant residual quadriceps weakness persists. Hennrikus et al3 examined quadriceps torque after conservative management of femoral fracture in 33 adolescent patients and found that 39% of these patients demonstrated persistent side-to-side quadriceps deficit of greater than 15% of the involved limb at an average of 33 months post injury. The authors attributed this finding to muscle damage sustained at the time of injury as quadriceps weakness correlated to the measured fracture displacement. Kapp et al7 evaluated the long-term deficits (mean 44 months) after IM nailing of femoral shaft fractures in 17 patients. Significant deficits were found in isometric quadriceps torque (18%) of the involved limb versus the uninvolved as measured on a dynamometer. Mira et al19 reported that only 17% of patients (5/29) demonstrated normal quadriceps function 16 months after fixation of femoral shaft fracture. These studies agreed with previous studies by Danckwardt-Lilliestrom,14 which reported quadriceps weakness up to 7 years post IM nailing. Conversely, Finsen et al20 studied a group of 14 isolated femoral shaft fracture patients who were treated with IM nailing. At a mean of 37 months, they noted loss of flexion torque but not extension torque. However, the authors noted that there was a large range of quadriceps deficit, and a correlation was observed between loss of quadriceps torque and time from surgery. Again, the authors of these studies have alluded to inadequate rehabilitation as a variable correlated to quadriceps strength after this injury; however, none have reported on this variable.7,14,19,20
Anterior Knee Pain
Anterior knee pain is also frequently reported after antegrade and retrograde nailing of the femur.4,6,21 Ostrum et al5 prospectively reported on 86 patients who sustained a femoral shaft fracture and were treated with an IM nail. The authors reported that approximately 12% of the patients complained of anterior knee pain at an average of 29 weeks postoperative. The authors postulated that the mechanism of knee pain was either damage to the patellofemoral (PF) cartilage at time of injury and/or quadriceps atrophy. Leggon and Feldmann6 reported on 19 patients with retrograde femoral nailing after isolated femoral fracture. At 19 months after surgery, 55% of the patients reported some knee pain with “diffuse” knee pain reported in 15% of the patients. Tornetta and Tiburzi21 cited a 59% rate of knee pain during rehabilitation but noted improvement with only 13% complaining once quadriceps strength had returned. Collectively, these authors attribute anterior knee pain to PF joint trauma at the time of injury,4 quadriceps weakness, or symptomatic hardware.4,6,21
Alteration in gait mechanics is a functional impairment often observed after IM nailing of femoral shaft fractures. This is typically attributed to hip abductor and quadriceps weakness. The use of computerized gait analysis22-24 has been used to objectively evaluate dynamic function of the lower extremities after femoral shaft fracture. Paterno et al24 longitudinally reported gait kinematic and kinetic findings in a case report of a patient after IM fixation of a femoral shaft fracture. The authors noted a substantial reduction in functional hip and knee motion 2 months after surgery. However, in subsequent analysis 8 months after surgery, the patient demonstrated improvement in hip kinematics but continued deficits in knee kinematics. These data suggested that improvement in hip function and resultant gait were possible, but residual deficits in knee kinematics and quadriceps activation remained 8 months after surgery.
In a more recent prospective longitudinal study, Archdeacon et al23 evaluated hip abductor function during gait after femoral fracture and antegrade nailing. At 2 months after surgery, hip abductor function related to gait was altered, yet theses deficits were significantly improved at 7 months postoperative. Interestingly, deficits in stride length and hip abductor function correlated significantly with the patient reported functional outcomes at 2 years after injury. This evidence suggests attempts to address gait impairments early in rehabilitation may result in improved long-term outcomes of patients after femur fractures.
Implications on Rehabilitation
Functional impairment including hip abduction weakness, quadriceps weakness, anterior knee pain, and resultant deficits in gait biomechanics have been observed after IM nailing of the femoral shaft fractures. These impairments result in a spectrum of presentations to the rehabilitation team and, consequently, to variable outcomes in regard to function and return to preinjury activities. Therefore, targeting rehabilitation intervention to address recognized impairments may lead to more predictable outcomes after femoral shaft fracture.
Historically, initiation of postoperative weight bearing (WB) after surgical fixation of femoral shaft fractures has been delayed until radiographic evidence of bony callous formation was present.25-29 Typically, this could extend up to 6-10 weeks postoperative, resulting in ambulation status remaining partial weight bearing (PWB) with use of an assistive device up to 3-4 months postoperative. Concurrently, the ability to progress rehabilitation beyond range of motion (ROM) and non-weight bearing (NWB) strengthening activities was somewhat limited resulting in exacerbation of postoperative impairments, ultimately leading to higher levels of functional deficits and disability, such as delayed return to work. More recent evidence suggests that early and immediate WB after surgical correction of femoral shaft fractures with fixation hardware of adequate strength is not only safe but also may facilitate fracture healing and promote more rapid time to union.24,25,30-34 Concurrently, initiation of immediate WB allows earlier initiation of physical therapy, a quicker progression to a full weight bearing (FWB) status independent of assistive device, and earlier initiation of progressive resistive exercises (PREs) to target strength and endurance impairments. However, it must be recognized that as the indications for IM nailing have expanded, the rehabilitation protocol, particularly early WB, may need to be reassessed. As an example, an intra-articular supracondylar femur fracture managed with an IM nail is not the same injury as a midshaft femur fracture managed with the same device, and the rehabilitation protocol must be individualized based on the injury and bony stability.
Ultimately, immediate WB has been postulated to result in less hospitalization with decreased need for prolonged in-patient rehabilitation and ultimately a decreased cost of care; however, this link has yet to be substantiated in the literature. Therefore, an aggressive physical therapy program with early WB may facilitate long-term success with patients undergoing IM nailing to quickly decrease the level of impairment that often leads to functional limitations and disability in these patients.
Rehabilitation after IM nailing of a femoral shaft fracture has been partitioned into 3 phases. Each phase is evaluation based and progression is dependent on successful attainment of baseline goals. These goals addressed WB status, knee effusion, leg edema, quadriceps control, hip abduction strength, and a normalization of gait. The program is a dynamic incorporation of WB progression, gait training, ROM activities, physical therapy modalities, stretching, PREs, balance, proprioception activities, and conditioning.24
Initiation of phase 1 (Table 1) of the femur fracture rehabilitation protocol begins postoperative day 1 in the hospital. Inpatient physical therapy consists of gentle ROM, initiation of a WB as tolerated (WBAT) ambulation program with an assistive device, and initiation of lower extremity isometrics. Upon discharge from the hospital, the patient is enrolled in an outpatient physical therapy program 2-3 d/wk.
Active range of motion and passive range of motion exercises of the lower extremity are initiated immediately after surgery. The initial focus is on attaining early full knee extension to decrease the risk of knee flexion contracture. This is achieved with posterior lower extremity stretching, including seated hamstring stretch and seated gastrocnemius stretching with the assistance of a towel. In addition, posterior knee stretching is attained by elevating the lower extremity with the heel propped up for 10 minutes 3-4 times per day (Fig. 1). This static heel propping stretch allowed for a low load, long duration stretch of the posterior knee. Knee flexion ROM exercise is also initiated immediately postoperatively.
Modalities are used at this time to attain 2 goals. First, neuromuscular reeducation with electrical stimulation is initiated postoperatively for the quadriceps muscle to help regain volitional control of the quadriceps (Fig. 1). Second, effusion and edema management may be addressed with the regular use of elevation and cryotherapy. Initial strengthening exercises focus on active control of knee extensor and hip abductor musculature to address these typical impairments. This can be initiated in a NWB position with open kinetic chain activities such as simple hip flexion, extension, and abduction exercises. A focus during these exercises should be to maintain a strong quadriceps contraction with the knee in a fully extended position. This is one of the initial attempts to recruit the quadriceps muscle and decrease the potential knee extensor lag often seen with femur fracture patients. Impaired hip abduction strength can also be targeted in an attempt to address functionally limiting deficits typically seen after femur fracture that leads to altered gait. In addition, active knee extension in a seated position, in an open kinetic chain, can be initiated without weight. This also can assist in return of isolated quadriceps activity. In addition to the focus on the proximal lower extremity musculature, distal lower extremity strength is also addressed, which includes a focus on gastrocnemius and soleus activation. This can be accomplished in a NWB position with the use of resistive bands and can ultimately be progressed to standing activities as the progression of WB will allow.
Initiation of balance and proprioception activities begins as WB is initiated. Simple weight shifting exercises without assistive devices to encourage increased comfort and confidence with progression of WB are initiated. These initial WB activities can quickly progress to include closed kinetic chain strengthening of the lower extremity. Mini squatting (Fig. 2) and toe raises can be initiated at this time to encourage a progressive increase in functional WB with both exercise and gait. Hip abduction is also a focus in early strengthening to address this impairment (Fig. 3). Gait training activities with assistive devices to promote knee flexion during swing phase of gait and normalization of a typical gait pattern are also initiated. A focus is placed on normalizing temporal spatial parameters, such as stride length, previously linked to long-term outcomes.23 As the patient progresses away from an assistive device, an increased focus is placed on controlling frontal plane trunk movements and a reduction of a Trendelenburg gait pattern. All these interventions are supplemented with a home exercise program, focused on hip and quadriceps strengthening. A targeted home program of progressive lower extremity and core strengthening activities in addition to a targeted gait retraining program may ultimately lead to an improved long-term outcome. Compliance with a targeted home exercise program designed to address known impairments that limit functional outcome will facilitate a more favorable outcome.
Before progression to phase 2, the patient must meet several baseline criteria. First, the patient must bear at least 50% of his weight with an assistive device during community ambulation. No more than minimal knee effusion and lower extremity edema must be present. With respect to muscle contraction and strength, the patient must demonstrate a fair quadriceps contraction and fair hip abduction strength. A fair quadriceps muscle contraction is defined as the ability to generate a superior patellar glide. This level of quadriceps contraction often results in an early resolution of an extensor lag at the knee with active hip flexion. A fair hip abduction strength is defined as the ability to elevate the lower extremity against gravity from the resting side-lying position. Successful attainment of these goals signifies an initial progression toward resolving known impairment that limits functional outcomes and results in progression to phase 2. Failure to meet these baseline criteria will result in additional time spent by the patient in the initial phase of rehabilitation.
Several interventions of phase 1 are progressed as appropriate into phase 2. A WBAT status is continued with the use of an assistive device, as needed for safe ambulation. The patient may progress to 1 crutch for assistance with balance during gait and may progress to no assistive devices when indicated. Use of neuromuscular reeducation with electrical stimulation may be continued to facilitate a volitional quadriceps contraction as indicated. General lower extremity stretching including gastrocnemius/soleus and hamstring stretching are encouraged.
A focus on progression of ROM continues in phase 2. Maintenance of full knee extension and progression of knee flexion activities are indicated until full functional ROM is attained. With the progression in WB status, there is also a progression in closed kinetic chain strengthening activities in phase 2. In addition, more NWB activities such as knee extension with ankle weights from 90 degrees of flexion to 30 degrees of flexion and hip abduction strengthening (Fig. 4) are continued with an increase in weights as tolerated.
Anterior knee pain has been identified as a potential limiting impairment in prior studies investigating outcomes after femur fractures.5 Therefore, care should be taken in the implementation and progression of exercises that could potentially place adverse stress on the PF joint. If evidence of PF joint pain or PF joint injury from the initial injury is present, a patella protection program should be instituted. This program would include an avoidance of activities such as deep squatting, repetitive loading of the PF joint, and activities that could cyclically load this region.
Balance, proprioception, and gait training activities are now be progressed. Proprioception activities including balance board activities, mini tramp marching, and WB PREs on an unstable surface are initiated at the end stages of phase 2. This includes single-leg toe raises, mini squatting, and simple perturbations on an unstable platform. Cardiovascular conditioning is also initiated at 6 weeks postoperative with the addition of stationary biking as adequate knee flexion is achieved.
Before progression to phase 3, the patient must meet several criteria. These criteria include FWB without assistive device, minimal effusion, fair to good quadriceps strength with a manual muscle test of 4+/5 and fair to good hip abduction strength with a manual muscle test of 4/5.
Phase 3 focuses on a progression of strength, normalization of gait, and an ultimate transition to desired activities. With respect to strengthening, the patient continues to increase the intensity of the exercises initiated in phase 2 through increased resistance with PREs. In addition, with the progression of WB to 100% without the use of an assistive device, the patient may begin single-leg strengthening activities, such as step-ups, half lunges, and single-leg mini squats. Deep knee flexion is avoided with these activities to limit irritation to the PF joint; however, they can be used with restrictions placed on knee flexion. Hip abduction strengthening is also progressed with more closed kinetic chain activities, such as resisted lateral walking. A continued focus is placed on functional limiting impairments, particularly knee extension and hip abduction activities.
Balance and proprioception activities are advanced to single-leg activities as FWB without assistive devices is achieved. Progression of static balance activities on stable platforms is progressed to more dynamic single-leg activities on stable and unstable platforms, and conditioning is progressed by incorporating treadmill walking. Treadmill walking should focus on training a more normal gait pattern, in addition to challenging the cardiovascular system.
Prior an ultimate progression back to all functional activities, the patient should progress through a return to activity phase. This targeted phase should be individually developed based on the physical capacities needed for the patient's specific return to function goals. Patient who plan a return to competitive sports activities should be guided through an appropriate return to sports progression, whereas those who plan to return to physically demanding employment should consider some type of work integration program. Participation in a focused intervention to assist the patient is developing activity-specific strength and skills will likely improve the long-term functional capacity and ultimate outcome for the patient. Care should be taken while developing this individualized transitional program to continue to focus on known strength and gait impairments that affect long-term outcomes.
At the conclusion of phase 3 and before discharge from formal rehabilitation, the patient should pass several baseline tests. With respect to gait, a normal gait pattern with no signs of Trendelenburg gait should be present. In addition, strength of the quadriceps and hip abductors should be assessed either clinically with manual muscle testing (grade 5 of 5 in strength) or with isokinetic dynamometry. Handheld dynamometry is an adequate substitute to objectify strength. A limb symmetry index of 85%-90% in both hip abductor and knee extensor and knee flexor strength is necessary to progress to discharge. When these baseline objective criteria are met and the patients successfully complete a return to sports or activity progression and an objective quantification of these skills, they are released from supervised physical therapy. This objective assessment of function may vary depending on the patient's goals. An athlete may need to progress through a return to sports program,35 whereas an industrial worker may need to complete a functional capacity evaluation. Once released to resume preinjury activities, a home exercise program aimed at functional progression toward preinjury work and recreational activities is recommended. Both the intensity and duration of the final steps of the end stages of this rehabilitation program may be greatly influenced by the type of work and activity to which the patient wishes to return.
Some consideration must be given to extenuating circumstances regarding injuries and the rehabilitation protocol. Patients with significant soft tissue wounds, whether open fractures, crush injuries, or even significant thigh contusions, may present a patient scenario that requires adaptation of the rehabilitation protocol. Flexibility will be necessary with these situations; however, every effort should be made to continue with a goals-based progression of the rehabilitation protocol, particularly, advancing to WBAT as quickly as possible because this really drives the progression of rehabilitation. In terms of segmental bone loss or even morbid obesity, we have allowed FWB with a planned bone grafting procedure for segmental loss. Modern implants are generally able to withstand FWB for 6-12 months even in the face of bone loss and/or excessive body weight. Similarly, patients with bilateral injuries are progressed through the protocol as much as possible, recognizing that some patients may be limited by pain. Finally, patients with multiple injuries, whether orthopaedic or otherwise, may have limitations that prevent advancement through the standard protocol. However, some components of the protocol may be useful, particularly the ROM and stretching exercises and the modalities for muscle reeducation.
The optimal surgical management of a femoral shaft fracture is well documented in the literature. IM nail fixation is the standard of care for skeletally mature patients with highly predictable union rates. Inconsistencies in care exist in the postoperative rehabilitation management, which may result in residual impairments known to lead to disability. Therefore, the development and implementation of a criterion-based rehabilitation practice guideline is necessary to help standardize care and improve patient outcomes. This practice guideline was designed specifically to target impairments recognized after IM nail stabilization of femoral shaft fractures. Future randomized control trials need to be implemented to validate this intervention and to optimize this treatment protocol.
1. Dartmouth Atlas examines lack of prevention in US health care. Continuum
2. Bain GI, Zacest AC, Paterson DC, et al. Abduction strength following intramedullary nailing of the femur. J Orthop Trauma
3. Hennrikus WL, Kasser JR, Rand F, et al. The function of the quadriceps muscle after a fracture of the femur in patients who are less than seventeen years old. J Bone Joint Surg Am
4. Ostrum RF, DiCicco J, Lakatos R, et al. Retrograde intramedullary nailing of femoral diaphyseal fractures. J Orthop Trauma
5. Ostrum RF, Agarwal A, Lakatos R, et al. Prospective comparison of retrograde and antegrade femoral intramedullary nailing. J Orthop Trauma
6. Leggon RE, Feldmann DD. Retrograde femoral nailing: a focus on the knee. Am J Knee Surg
7. Kapp W, Lindsey RW, Noble PC, et al. Long-term residual musculoskeletal deficits after femoral shaft fractures treated with intramedullary nailing. J Trauma
8. Karumo I. Intensive physical therapy after fractures of the femoral shaft. Ann Chir Gynaecol
9. Bednar DA, Ali P. Intramedullary nailing of femoral shaft fractures: reoperation and return to work. Can J Surg
10. Wolinsky P, Tejwani N, Richmond JH. Controversies in intramedullary nailing of femoral shaft fractures. J Bone Joint Surg Am
11. Jurkovich G, Mock C, MacKenzie E, et al. The Sickness Impact Profile as a tool to evaluate functional outcome in trauma patients. J Trauma
12. Butcher JL, MacKenzie EJ, Cushing B, et al. Long-term outcomes after lower extremity trauma. J Trauma
13. Wolinsky P, Tejwani N, Richmond JH, et al. Controversies in intramedullary nailing of femoral shaft fractures. J Bone Joint Surg
14. Danckwardt-Lilliestrom G, Sjogren S. Postoperative restoration of muscle strength after intramedullary nailing of fractures of the femoral shaft. Acta Orthop Scand
15. Winquist RA, Hansen ST Jr, Pearson RE. Closed intramedullary shortening of the femur. Clin Orthop
16. Winquist RA, Hansen ST Jr, Clawson DK. Closed intramedullary nailing of femoral fractures. A report of five hundred and twenty cases. J Bone Joint Surg Am
17. Nichols P. Rehabilitation after fractures of the shaft of the femur. J Bone Joint Surg Br
18. Zdravkovic D, Damholt V. Quadriceps function following indirect nailing of femoral shaft fractures. Acta Orthop Scand
19. Mira AJ, Markley K, Greer RB III. A critical analysis of quadriceps function after femoral shaft fracture in adults. J Bone Joint Surg Am
20. Finsen V, Svenningsen S, Harnes OB, et al. Osteopenia after plated and nailed femoral shaft fractures. J Orthop Trauma
21. Tornetta P III, Tiburzi D. Antegrade or retrograde reamed femoral nailing. A prospective randomised trial. J Bone Joint Surg Br
22. Wong J, Boyd R, Keenan NW, et al. Gait patterns after fracture of the femoral shaft in children, managed by external fixation or early hip spica cast. J Pediatr Orthop
23. Archdeacon M, Ford KR, Wyrick J, et al. A prospective functional outcome and motion analysis evaluation of the hip abductors after femur fracture and antegrade nailing. J Orthop Trauma
24. Paterno MV, Archdeacon MT, Ford KR, et al. Early rehabilitation following surgical fixation of a femoral shaft fracture. Phys Ther
25. Arazi M, Ogun TC, Oktar MN, et al. Early weight-bearing after statically locked reamed intramedullary nailing of comminuted femoral fractures: is it a safe procedure? J Trauma
26. Bucholz RW, Ross SE, Lawrence KL. Fatigue fracture of the interlocking nail in the treatment of fractures of the distal part of the femoral shaft. J Bone Joint Surg Am
27. Franklin JL, Winquist RA, Benirschke SK, et al. Broken intramedullary nails. J Bone Joint Surg Am
28. Kempf I, Grosse A, Beck G. Closed locked intramedullary nailing. Its application to comminuted fractures of the femur. J Bone Joint Surg Am
29. Riemer BL, Foglesong ME, Miranda MA. Femoral plating. Orthop Clin North Am
30. Brumback RJ, Toal TR Jr, Murphy-Zane MS, et al. Immediate weight-bearing after treatment of a comminuted fracture of the femoral shaft with a statically locked intramedullary nail. J Bone Joint Surg Am
31. Einhorn TA. Enhancement of fracture-healing. J Bone Joint Surg Am
32. Foster TE, Healy WL. Operative management of distal femoral fractures. Orthop Rev
33. Hulth A. Current concepts of fracture healing. Clin Orthop Relat Res
34. Meadows TH, Bronk JT, Chao YS, et al. Effect of weight-bearing on healing of cortical defects in the canine tibia. J Bone Joint Surg Am
35. Myer GD, Paterno MV, Ford KR, et al. Rehabilitation after anterior cruciate ligament reconstruction: criteria-based progression through the return-to-sport phase. J Orthop Sports Phys Ther