Long-Term Outcome of Step-Cut Ulnar Shortening Osteotomy for Ulnar Impaction Syndrome

Papatheodorou, Loukia K. MD, PhD; Baratz, Mark E. MD; Bougioukli, Sofia MD; Ruby, Tyler; Weiser, Robert W. MPAS, PA-C; Sotereanos, Dean G. MD

Journal of Bone & Joint Surgery - American Volume:
doi: 10.2106/JBJS.15.01111
Scientific Articles
Abstract

Background: Extra-articular ulnar shortening osteotomy is a common procedure for the surgical treatment of ulnar impaction syndrome. Several techniques for this osteotomy have been developed to avoid the morbidity associated with a standard transverse osteotomy. However, these techniques require special instrumentation and are expensive. The purpose of this study was to evaluate the outcome of step-cut ulnar shortening osteotomy without special jigs for ulnar impaction syndrome.

Methods: A retrospective study of 164 consecutive patients who underwent step-cut ulnar shortening osteotomy between 2000 and 2010 was performed. The long arm of the step-cut osteotomy was oriented in the coronal plane parallel to the long axis of the ulna. The short arms of the osteotomy were perpendicular to the long axis in the axial plane. Fixation was performed with a palmar 3.5-mm standard neutralization plate and a lag screw. The goal of the osteotomy was to reduce ulnar variance, which was assessed in all patients with pronated grip-view radiographs preoperatively and postoperatively. Preoperative ulnar variance ranged from +1 to +6 mm.

Results: All patients were followed for at least 24 months. Union of the osteotomy site was achieved at a mean of 8.2 weeks. The union rate was 98.8%. There were 2 cases of nonunion, which required additional surgery. The mean postoperative ulnar variance was +0.2 mm (range, −1 to +1.5 mm) after a mean overall ulnar shortening of 2.5 mm. All patients returned to their previous work, in a mean of 4 months. The plate was removed from 12 patients because of plate-related symptoms. No other complications were encountered.

Conclusions: The step-cut ulnar shortening osteotomy provides ample bone-to-bone contact and simplifies control of rotation. Stable internal fixation with standard techniques allowed an early return to functional activities. Palmar placement of the plate diminishes the need for plate removal. This is a simple and less expensive technique for ulnar shortening that does not require the use of special instrumentation in patients with ulnar impaction syndrome.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Author Information

1University of Pittsburgh, Orthopaedic Specialists–UPMC, Pittsburgh, Pennsylvania

2University of Southern California, Keck School of Medicine, Los Angeles, California

3University of Pittsburgh, Pittsburgh, Pennsylvania

E-mail address for L.K. Papatheodorou: loukiapapath@yahoo.gr

E-mail address for M.E. Baratz: mebaratz@gmail.com

E-mail address for S. Bougioukli: Sofia.Bougioukli@med.usc.edu

E-mail address for T. Ruby: tor6@pitt.edu

E-mail address for R.W. Weiser: weiserrw@ph.upmc.edu

E-mail address for D.G. Sotereanos: dsoterea@hotmail.com

Article Outline

Ulnar impaction syndrome, or ulnocarpal abutment syndrome, is characterized as a degenerative condition of the ulnar side of the wrist related to excessive load-bearing between structures of the ulnocarpal joint1. It is frequently associated with positive ulnar variance, which can be congenital (idiopathic) or secondary to malunion of a distal radial fracture, early physeal arrest of the distal part of the radius, a previous Essex-Lopresti injury, or radial head resection.

Ulnar shortening osteotomy is a common and widely accepted procedure for the surgical treatment of ulnar impaction syndrome. Extra-articular ulnar shortening osteotomy can unload the ulnocarpal joint, preserving the cartilage surface at the distal part of the ulna while the ulnocarpal ligaments are tightened2.

Many types of ulnar shortening osteotomy and several fixation techniques have been described3-13. Transverse osteotomies require perfectly parallel cuts to ensure proper bone rotational alignment and contact to prevent malunion or nonunion3-7. Oblique osteotomies allow a greater surface area of contact, facilitating bone healing. However, accurately parallel cuts are required and difficulties can be encountered with rotational control and lag-screw placement8-13. Furthermore, many surgeons utilize techniques that require special instrumentation to achieve accurate shortening.

To avoid the difficulties with the bone contact and rotational control associated with transverse or oblique osteotomies and to eliminate the cost of specialized equipment, the senior author began using step-cut ulnar shortening osteotomy, and he and colleagues previously reported promising early results14. The purpose of this study was to evaluate the mid-term to long-term outcomes of step-cut ulnar shortening osteotomy without special jigs or instrumentation for ulnar impaction syndrome.

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Materials and Methods

Between 2000 and 2010, 164 patients underwent step-cut distal ulnar shortening osteotomy for ulnar impaction syndrome by the 2 senior authors. After institutional review board approval, we retrospectively reviewed the medical data of these patients. Eighty-eight patients were female and 76 were male. The mean age at the time of the ulnar shortening osteotomy was 36.8 years (range, 14 to 59 years). Fifty-eight patients used tobacco products. The dominant arm was involved in 93 patients (Table I).

All patients presented with ulnar-sided wrist pain. All had pain with the ulnocarpal stress test15, which was performed with maximum ulnar deviation with the wrist pronated and then flexed and extended. All patients also had positive ulnar variance as depicted by pronated grip-view radiographs16. The x-ray beam was placed 1 m from the table and was aligned perpendicular to the radial styloid in the sagittal and transverse planes. The preoperative ulnar variance ranged from +1 to +6 mm with a mean of +3.5 mm. One hundred and sixteen patients had symptomatic idiopathic ulnar impaction syndrome. Forty-eight patients had a history of trauma, with 35 of them having undergone previous surgery for the injury (Table II).

Wrist arthroscopy was performed prior to the ulnar shortening osteotomy, during the same operative session, in the majority (138) of the patients. Wrist arthroscopy was used to verify the diagnosis or treat concurrent intra-articular lesions such as scapholunate or lunotriquetral ligament tears and attritional tears of the triangular fibrocartilage complex.

The step-cut ulnar shortening osteotomy was performed in all patients by the 2 senior authors. The goal was to reduce ulnar variance by shortening the ulna a few millimeters and not necessarily to create neutral or negative ulnar variance. The step-cut ulnar shortening osteotomy was performed as previously described14 and as summarized below.

The procedure is performed with the arm either on a hand-table extension or placed in a traction tower if wrist arthroscopy precedes the ulnar shortening osteotomy. Through an 8-cm longitudinal skin incision along the distal third of the ulna, the interval between the extensor carpi ulnaris and the flexor carpi ulnaris is utilized for exposure of the distal part of the ulna.

The long arm of the step-cut osteotomy is oriented in the coronal plane parallel to the long axis of the ulna (Fig. 1-A), and the short arms are perpendicular to the long axis in the axial plane. A 7-hole 3.5-mm standard neutralization plate is used as a template to design the osteotomy. Care is taken to apply the plate palmar and proximal enough on the ulna to avoid impingement of the plate or screws into the distal radioulnar joint with rotation of the forearm. The distal part of the plate should be placed approximately 1 to 2 cm proximal to the ulnar head. The long arm of the osteotomy, approximately 15 to 20 mm in length, is marked at the midportion of the plate between the third and fifth holes, allowing placement of bicortical screws in these 2 holes (Figs. 1-B and 2).

The long arm of the osteotomy is created with an oscillating saw along the long axis of the ulna, cutting through both cortices. Then, the 2 short arms are created perpendicular to the long cut, dividing the ulna into dorsal and volar halves as opposed to radial and ulnar halves (Fig. 1-B). Both ends (proximal and distal) of the osteotomized ulna are shortened approximately 2 to 4 mm by cutting parallel to the initial short-arm osteotomies. Next, the osteotomy site is reduced and a lag screw is placed across and central to the osteotomy from dorsal to volar and perpendicular to the long arm of the osteotomy to compress the arms of the osteotomy. The lag screw is placed from dorsal to volar to allow ease of perpendicular screw placement. Finally, the osteotomy site is fixed with the 7-hole 3.5-mm standard neutralization plate on the volar surface of the ulna, with 3 screws proximal and 3 screws distal to the lag screw (Fig. 2). The shortening is provided by the bone removal at each limb of the horizontal osteotomy. The lag screw provides compression at the vertical osteotomy site, and the plate is used for neutralization.

Postoperatively, the wrist is immobilized with a short arm splint for the first 2 weeks, after which the wrist is placed in a short arm removable splint. Active range-of-motion exercises are initiated at 6 weeks, and weight-bearing is allowed after there is clinical and radiographic evidence of osseous union.

All patients underwent subjective and objective evaluations before and after the surgery. The pain level was indicated on a visual analog scale (VAS) ranging from 0 cm (no pain) to 10 cm (maximal pain). The wrist range of motion was assessed with a goniometer. Grip strength was measured using a Jamar dynamometer (Preston), and the values were recorded as a percentage of the strength on the contralateral (unaffected) side. Wrist function was assessed using the Mayo Modified Wrist Score (MMWS).

In all patients, the healing progress was evaluated clinically and radiographically at the first postoperative visit at 2 weeks and then approximately every 4 to 6 weeks. Union was defined as trabecular bone bridging the osteotomy site with blurring of the cortical margins of the osteotomy, seen on posteroanterior, lateral, and oblique radiographs, in combination with a clinical absence of tenderness to direct palpation at the osteotomy site8 by the 2 senior authors. At 6 weeks postoperatively, a pronated grip-view radiograph was obtained to assess ulnar variance. We compared preoperative and postoperative pronated grip-view radiographs to depict the amount of ulnar shortening.

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Statistical Analysis

For statistical purposes only, the patients were divided into 3 groups based on their postoperative ulnar variance (negative, neutral, or positive) to determine whether there was an association between postoperative ulnar variance and the postoperative outcome with regard to pain, grip strength, wrist range of motion, and MMWS.

Statistical analysis was done with IBM SPSS Statistics 22 with the significance level set at 0.05. Descriptive statistics are given for the overall cohort and also according to the postoperative ulnar variance and are reported as the mean and standard deviation or range. The related-samples Wilcoxon signed rank test was used for the comparison of preoperative and postoperative values. The Kruskal-Wallis test was used to compare postoperative pain, wrist range of motion, grip strength, and MMWS score among patients with different postoperative ulnar variance values. The Fisher exact test was used to determine whether there was an association between asymptomatic postoperative arthritis of the distal radioulnar joint and performance of wrist arthroscopy during the ulnar shortening procedure and between asymptomatic postoperative arthritis of the distal radioulnar joint and postoperative ulnar variance values.

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Results

All patients in whom wrist arthroscopy was performed (138 of 164) were found to have a central triangular fibrocartilage complex tear and chondromalacia of the lunate. A tear of the lunotriquetral ligament was observed in 67 patients. These concurrent injuries were addressed solely with arthroscopic debridement prior to the ulnar shortening osteotomy.

All patients were followed for at least 24 months (median, 66 months; range, 24 to 86 months). The union rate was 98.8% (162 of 164 patients). The mean time until the 162 patients showed clinical and radiographic evidence of union (Fig. 3) was 8.2 weeks (range, 5 to 18 weeks), with union seen by 8 weeks in 82% of the patients, by 10 weeks in 95%, and by 18 weeks in all patients except 2 with persistent pain who had nonunion diagnosed radiographically and clinically. One of these 2 patients was a heavy smoker, and the other was a nonsmoker. At 6 months postoperatively, both patients underwent additional surgery with autologous iliac crest bone-grafting at the osteotomy site and maintenance of the plate. Both nonunions healed, at 10 and 11 weeks after the revision surgery.

The range of postoperative ulnar variance overall was between −1 and +1.5 mm, with a mean of +0.2 mm (Table III and Fig. 4). The mean amount of ulnar shortening was 2.5 mm (range, 2 to 5 mm) overall, 2.3 mm (range, 2 to 4 mm) in patients with idiopathic ulnar impaction syndrome, and 2.7 mm (range, 2 to 5 mm) in patients with posttraumatic ulnar impaction syndrome. At the time of final follow-up, asymptomatic degenerative changes of the distal radioulnar joint were noted on radiographs of 9 patients (5.5%)—3 with idiopathic ulnar impaction syndrome and 6 with posttraumatic ulnar impaction syndrome. Of these 9 patients, 2 with a previous Essex-Lopresti injury were observed to have very mild degenerative arthritic changes of the distal radioulnar joint, with mild osteophyte formation along the proximal margin of the ulnar head, on preoperative radiographs. After the ulnar shortening osteotomy, we noted worsening of these preoperative changes. No patient had symptomatic arthritis of the distal radioulnar joint during the follow-up period.

All patients had significant postoperative improvement with respect to pain, range of motion, grip strength, and MMWS (p < 0.001) regardless of the postoperative ulnar variance (i.e., negative, neutral, or positive) (Table IV and Fig. 5). There was no significant association between asymptomatic postoperative distal radioulnar joint arthritis and the postoperative (negative, neutral, or positive) ulnar variance. Furthermore, no significant difference with respect to the development of distal radioulnar joint arthritis was observed between patients in whom wrist arthroscopy had been performed at the same time as the step-cut ulnar shortening osteotomy and those in whom it had not. All patients returned to their previous work postoperatively, at a mean of 4 months (range, 3 to 10 months).

Twelve patients (7.3%) had the plate removed because it was causing irritation. The removal was performed at least 18 months after the ulnar shortening osteotomy to reduce the risk of refracture7,10,17. There were no other complications except for the 2 nonunions described earlier.

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Discussion

Extra-articular ulnar shortening osteotomy has been widely used to manage positive ulnar variance in symptomatic patients with ulnar impaction syndrome. Many techniques for this osteotomy have been proposed, including those using special jigs, cutting guides, or shortening systems and different forms of fixation3-13. However, no technique has demonstrated clinical superiority.

The step-cut ulnar shortening osteotomy was designed to overcome the difficulties with rotational control experienced with transverse or oblique osteotomy and to decrease cost by avoiding the need for special instrumentation. The step-cut configuration of the ulna provides ample bone-to-bone contact, facilitating healing and control of rotation. Stable internal fixation in combination with rapid healing allows early wrist mobilization.

The current cohort demonstrated improvement in pain scores and wrist function as well as rapid healing postoperatively, confirming the efficacy of the step-cut ulnar shortening osteotomy. The MMWS improved in all patients, by a mean of 41.5 points. All patients returned to their previous work, at a mean of 4 months postoperatively.

Authors of previous studies have reported nonunion rates as high as 13% after ulnar shortening osteotomy8,18. In our large serial study of 164 patients, only 2 nonunions (1.2%) were noted and both healed after secondary surgery with autologous iliac crest bone-grafting. Although it is difficult to compare the actual times to union among the various studies, because of different radiographic criteria for defining union, it was usually achieved within 5 months regardless of the type of osteotomy. In the current study, the mean time to union was 8.2 weeks (range, 5 to 18 weeks), which compares favorably with the results of previous clinical studies.

Plate irritation is the most common complication leading to a reoperation after ulnar shortening osteotomy. In the current large serial cohort, the plate was removed from only 12 (7.3%) of 164 patients, whereas the implant removal rate after ulnar shortening osteotomy has been reported to be as high as 55%5,10,11,18-21. Iwasaki et al.19 documented a 55% plate removal rate in their cohort of 53 cases. In a study by Chen and Wolfe11, the plate was removed from 8 (44%) of 18 patients, and Pomerance20 reported a rate of implant removal of 35% in 40 patients. In the current cohort of patients treated with a step-cut osteotomy, the volar placement of the plate on the ulna diminished the need for plate removal. We believe that this is due to better soft-tissue coverage of the plate with volar placement. In addition, with use of techniques that require a jig, there is the potential for more extensive periosteal stripping of the ulna, which may increase the nonunion rate.

Distal radioulnar joint arthritis has been reported to develop in up to 38% of patients who have undergone ulnar shortening osteotomy7,18,22. However, the majority of patients with radiographic evidence of distal radioulnar joint arthritis are asymptomatic. Baek et al.22 reported that 6 (17%) of 36 patients developed arthritic changes in the distal radioulnar joint after ulnar shortening osteotomy, and Minami and Kato7 noted radiographic signs of distal radioulnar joint arthritis in 7 (28%) of 25 patients at a mean of 35 months. They determined the optimal amount of ulnar shortening to be a mean of 3 mm to obtain neutral ulnar variance7. Köppel et al.18 observed arthritic changes of the distal radioulnar joint in 18 (38%) of 47 patients at a mean of 18 months after ulnar shortening osteotomy, the goal of which was correction to 2 mm of negative ulnar variance. They found that the ulnar variance was reduced from a mean of +1.5 mm (range, −2 to +15 mm) preoperatively to a mean of −2.1 mm (range, −4 to +4 mm) postoperatively.

In a biomechanical study, Nishiwaki et al.2 suggested that there is some correlation between the amount of ulnar shortening and the development of distal radioulnar joint arthritis, as they found that the pressure at the distal radioulnar joint increased as the amount of the ulnar shortening increased.

Baek et al.22 reported a significant association between the amount of ulnar shortening and the development of distal radioulnar joint arthritis. They retrospectively reviewed the cases of 36 patients with idiopathic ulnar impaction syndrome. The goal of the ulnar shortening osteotomy was to obtain neutral to 2 mm of negative ulnar variance. They reported a high prevalence of arthritic changes of the distal radioulnar joint at a minimum of 5 years postoperatively in patients who underwent greater ulnar shortening. The mean ulnar shortening was 7.0 ± 2.0 mm in 6 patients with postoperative distal radioulnar joint arthritis and 4.8 ± 2.1 mm in 30 patients without such postoperative arthritic changes. However, intra-articular fractures of the distal radioulnar joint may also influence the congruity of the distal radioulnar joint and contribute to the development of arthritis at that joint.

In our retrospective review of 164 patients with idiopathic or posttraumatic ulnar impaction syndrome, we found that the step-cut ulnar shortening osteotomy resulted in a lower rate of degenerative changes at the distal radioulnar joint compared with rates reported in previous studies7,18,22. In our study, in which the median duration of follow-up was 66 months, asymptomatic degenerative changes of the distal radioulnar joint were noted on radiographs of 9 (5.5%) of the 164 patients. We believe that the reason for the lower rate of degenerative changes of the distal radioulnar joint in the current cohort is the smaller amount of ulnar shortening. The mean amount of ulnar shortening was 2.5 mm. Our goal was to unload the ulnocarpal joint by shortening the ulna by only a few millimeters and not necessarily to reduce ulnar variance to neutral. We strongly believe that this diminishes the rate of articular incongruity and hence arthritis of the distal radioulnar joint. However, the actual prevalence of distal radioulnar joint arthritis after ulnar shortening osteotomy still needs to be determined with longer follow-up since the arthritis may develop at a later time point.

The results of our statistical analysis also showed step-cut ulnar shortening osteotomy to be an effective method for decreasing pain and improving wrist function in patients with ulnar impaction syndrome, regardless of whether the postoperative ulnar variance is negative, neutral, or positive.

Our current cohort demonstrated that step-cut ulnar shortening osteotomy with a 7-hole 3.5-mm standard neutralization plate and a lag screw for fixation provides good-to-excellent functional results without the need for expensive surgical equipment. Although the outcomes of previous studies5,8,10,13,17 of ulnar shortening osteotomies done with special surgical devices were comparable with those in our current cohort, there is a noteworthy difference regarding the cost of the devices. At our institution, the cost for special ulnar osteotomy systems is almost 10 times higher than that for a 7-hole 3.5-mm standard neutralization plate.

The current study was limited by its retrospective nature and the absence of a control group. However, we found successful healing and a very low rate of implant removal in a large series of 164 ulnar shortening osteotomies performed by 2 surgeons and followed for a median of 66 months.

This study demonstrates that the step-cut ulnar shortening osteotomy is a safe and reliable technique resulting in rapid healing and an early return to functional activities. The volar placement of the plate diminishes the need for implant removal. The step-cut ulnar shortening osteotomy is a simple and less expensive technique that utilizes a 7-hole 3.5-mm standard neutralization plate and a lag screw for fixation, thereby avoiding the need for special instrumentation.

Investigation performed at the University of Pittsburgh, Orthopaedic Specialists–UPMC, Pittsburgh, Pennsylvania

Disclosure: No funding was received for this study. The Disclosure of Potential Conflicts of Interest forms are provided with the online version of this article.

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