Although the primary goal of total knee arthroplasty (TKA) is pain relief, restoration of function and specifically the attainment of high flexion have emerged as an important secondary goal. During the past several decades, authors have been open to continual evaluation and evolution of clinical pathways that focus on improvement in restoration of function in the treatment of patients with total joint arthroplasty.4,48,49,51,52 These have involved the refinement of the entire perioperative process both for the patient and family.
We have adopted office and hospital procedures that focus on rapid recovery. Patients are advised from the initial evaluation they will be able to quickly return to activities of daily living. Two decades ago, it was not uncommon to restrict patients to bed rest for 24 hours after surgery and avoid activities requiring range of motion (ROM) until 2 to 3 days after surgery. Currently, patients are out of bed within hours of surgery, commencing activities that require ROM. Most patients are discharged directly home within 24 to 48 hours. We have previously reported adopting aggressive clinical pathways has led to an earlier attainment of postoperative milestones for patients undergoing primary total knee arthroplasty.4,49
Having appreciated the incremental benefits of rapid recovery protocols on restoration of function after TKA, we sought to determine if a less invasive mini-arthrotomy approach could further reduce length of stay, enhance ROM, reduce pain and increase functional scores at followup.
MATERIALS AND METHODS
From May 2003 to February 2005, we performed 203 consecutive TKAs using the Vanguard Complete Knee System (Biomet Inc, Warsaw, IN). All implants were fixed with cement. Posterior cruciate retaining implants were used in most patients (97%), with posterior stabilized devices used in the remainder. During the time frame of the study, microplasty instrumentation was introduced, and the authors began using a less invasive mini-arthrotomy approach. Therefore, the patients constituted two groups based on surgical approach. Group 1, the initial group, comprised 88 patients undergoing 106 TKAs performed through a standard median parapatellar arthrotomy. Group 2 consisted of 76 patients undergoing 97 TKAs performed using a less invasive mini-arthrotomy approach with Microplasty (Biomet Inc, Warsaw, IN) instrumentation. There were 107 women (65%) and 57 men (35%) in the entire series of patients with no difference in the male to female ratio between Groups 1 and 2. The primary diagnosis was osteoarthritis in most patients (97%). Other diagnoses included posttraumatic arthritis (five patients; .5%) and osteonecrosis (one patient; 0.5%). Patients with rheumatoid arthritis, multiple skin incisions, and revision procedures were excluded from this review. Overall, bilateral procedures were performed simultaneously under a single anesthetic in 25 patients, and in a staged fashion in 16 patients. Two women who underwent staged bilateral procedures had one knee in each group. There was no difference in distribution of underlying diagnoses, incidence of bilateral procedures, or application of prosthetic constraint between groups. The average age of the entire cohort was 65 years (range, 39-89 years). Patient age was similar between groups (64 years in Group 1 and 66 years in Group 2). The average height for the overall series was 1.68 m (66 inches), average weight was 95.7 kg (211 pounds), and average body mass index (BMI) was 34. Although patients were not excluded from a mini-arthrotomy for obesity, patients in Group 1 had a higher (p = 0.01) average BMI than those in Group 2 (35 versus 33, respectively). The incidence of preoperative fixed flexion deformity more than 20°, flexion at less than 90°, valgus deformity, severity of varus deformity were similar between both groups. The average preoperative flexion was similar in Groups 1 and 2 (106° versus 109°, respectively). All patients were managed perioperatively using identical rapid recovery pathways (Table 1).
Radiographic review on immediate postoperative radiographs was performed by two independent observers (KLG, JHR) in a blinded fashion to surgical approach. Extraneous cement retention, cement mantle quality, femoral alignment, tibial alignment, overall limb alignment, lateral patellar tilt, notching of the femur, and tibial implant sizing were examined.
Statistical analyses were performed using StatsDirect (Stats Direct, Ltd; Cheshire, UK). All analyses were performed using 95% confidence intervals (CI) (p = 0.05). Unpaired student's t test was used to evaluate parametric data including differences in patient age, weight, body mass index, operative time, estimated blood loss, length of hospital stay, ROM, and clinical scores. Chi squared two-by-two analyses were used to evaluate differences between groups in incidence of preoperative fixed flexion deformity greater than 20°, flexion arc less than 90°, valgus deformity, or severity of varus deformity, discharge disposition, ability to meet rehabilitation milestones, and incidence of radiographic variances. Power analysis was performed using 80% power to detect a significant difference and an alpha error or significance defined as p < 0.05 for the primary research variable of post-operative range of motion. Based on a clinically justifiable difference in range of motion of 5 degrees between groups, the current study contains ample power to detect a significant difference. To obtain the stated power, 60 patients in the mini-group, and 65 patients in the open group would be needed.
The length of hospital stay in Group 2 was shorter (p < 0.001) than for patients in Group 1 (average stay 2.7 days for Group 1 versus 2.2 days for Group 2). More (p = 0.0002) patients in Group 2 (18 of 82 admissions, 22%) than in Group 1 (4 of 96 admissions, 4%) were discharged directly to home on the first postoperative day. More (p = .04) patients in Group 2 (52 of 82 admissions, 63%) than in Group 1 (46 of 96 admissions, 48%) were discharged to home within 48 hours of surgery. No patient in Group 2 stayed longer than 4 days, whereas two patients in Group 1 had longer stays. A higher (p = 0.01) percentage of patients in Group 2 (42%) compared with patients in Group 1 (26%,) were discharged to home with arrangements for outpatient physical therapy rather than discharge to an extended care facility or home with arrangements for in-home health and therapy services.
Despite earlier discharge from the hospital and less reliance on inpatient rehabilitation facilities and in-home physical therapy, Group 2 obtained higher (p = 0.004) average arc of motion at 6-week followup than Group 1 (111° versus 105°). A higher (p = 0.02) proportion of patients in Group 2 achieved ROM greater than 120° by 6 weeks after surgery than in Group 1 (31% versus 17%).
A higher (p = 0.01) proportion of patients had mild or absent pain at 6 weeks in Group 2 (84%) when compared with Group 1 (69%). Most recent followup was similar between the groups, averaging 11 months in Group 1 and 9 months in Group 2. Differences in ROM and Knee Society clinical scores were observed at most recent followup. Group 2 had higher average ROM (p = 0.02), Knee Society clinical score (p = 0.006), and Knee Society pain subscore (p = 0.003) than Group 1 at most recent followup. Arc of motion for Groups 1 and 2 averaged 112° and 116°, respectively, whereas Knee Society clinical scores averaged 85 and 90, respectively, and pain sub-scores averaged 38 and 43, respectively. There were no differences between the two groups in any radiographic parameters examined, including component sizing, component and limb alignment, cement mantle quality, and incidence of cement retained in the joint space.
Perhaps one of the most concrete methods of assessing restoration of function is the attainment of a full and satisfactory ROM. Several studies document normal ROM of the human knee is 0° to 140°.33,40,80 The elements affecting ROM are multifactorial and involve patient-specific characteristics, perioperative management, surgical technique, and prosthetic-specific issues. The authors have previously reported on a number of these topics. An aggressive approach to perioperative pain management using multimodal techniques enhances postoperative rehabilitation. A multidisciplinary interactive system approach positively influences patient recovery (Table 1). Clearly there has been sufficient literature to support the multiple aspects of this systematic approach to the perioperative care and treatment of patients undergoing TKA.
We did not use a prospective or randomized design. However, multiple studies document the most important determinant of postoperative ROM is the preoperative ROM and preoperative flexion arc.1,7,27,32,35,37,47,53,63,70,71 In our patients the preoperative ROM and flexion arc were similar in both groups. The same perioperative protocol and TKA implant system was used in all cases. The major difference was a standard arthrotomy versus a mini-arthrotomy.
Clearly, patients in Group 2 attained a greater ROM sooner and maintained that ROM. Minimizing iatrogenic trauma in unicompartmental knee arthroplasty to the suprapatellar pouch facilitates a more rapid attainment of postoperative milestones.65,68,69 Repicci69 reported a minimally invasive approach decreased the need for postoperative physical therapy. Price et al65 showed minimally invasive unicondylar knee arthroplasty with the Oxford mobile bearing device will effectively enhance the patients' ability to recover from the operative intervention without having an impact on outcome.34,68 Although it may be almost impossible to avoid damaging the supracondylar pouch iatrogenically in total knee arthroplasty, efforts have been made to minimize trauma to the suprapatellar pouch using several different approaches including the quadriceps-sparing approach,81 limited medial parapatellar arthrotomy,73,79 mini midvastus approach,25,38,39 and a mini subvastus approach.5 The common theme to all of these approaches is a smaller skin incision with attention to minimizing surgical trauma to the suprapatellar pouch and the extensor mechanism by limiting the surgical dissection into the extensor mechanism and by avoiding eversion of the patella. These authors have reported decreased postoperative pain, improved quadriceps function, and improvement in postoperative ROM. Laskin et al39 compared 32 TKAs performed through a mini midvastus approach without patellar eversion to 26 TKAs performed with a standard medial parapatellar approach. They reported improved flexion with the minimally invasive technique at 6 days and at 6 weeks. However, there were no differences between the groups at 3 months. Haas et al25 compared 40 TKAs performed with a mini midvastus arthrotomy without patellar eversion to 40 TKAs performed with a standard medial parapatellar approach. Patients treated with a minimally invasive technique had improved flexion at 6 weeks and at 1 year after surgery.
Based on our previous reports, the implementation of clinical pathways focused on rapid recovery assists the patient in obtaining earlier increased knee scores with improved early postoperative ROM without increasing postoperative complications.4,48,49,51,52 The current study shows minimization of iatrogenic trauma also facilitates the early attainment of postoperative ROM. However, it remains our opinion a rapid recovery program is multifactorial and involves a thorough and complete preoperative evaluation and alignment of expectations of the surgeon, patient and family, preoperative education, preoperative physical therapy, optimization of the condition of the patient, effective perioperative pain management, efficient and accurate surgery with minimally invasive techniques, early mobilization and activities requiring ROM, and aggressive postoperative physical therapy protocols. In addition to the goal of pain relief, restoration of function as measured by the attainment of early and enhanced ROM has emerged as an important goal of TKA. The entire perioperative process for the patient and family, including office and hospital procedures, has been refined to facilitate a rapid return to activities of daily living after TKA.
A retrospective review of a standard arthrotomy group and a mini-arthrotomy group, both treated perioperatively with similar aggressive multifactorial rehabilitation protocols, revealed mini-arthrotomy group patients were discharged home sooner and achieved a higher ROM at 6 weeks, which was sustained at most recent follow up along with improved clinical and pain scores.
The authors gratefully acknowledge the efforts of Kari L. Groseth, BS, and Jackie H. Russell, RN, in performing the radiographic review reported, and Joanne B. Adams, BFA, and Tawnya L. Tucker, MT, for their assistance in preparing this manuscript.
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