Effects of wafer resection and hemiresection from the distal ulna on load-sharing at the wrist: a cadaveric study

Reverse Wafer Procedure for Ulnar Impaction Syndrome

Ulnar impaction syndrome occurs when excessive load across the ulnocarpal joints results in pathologic changes, especially over the articular surface of the ulnar head and proximal ulnar corner of the lunate. The 2 main surgical options in ulnar impaction syndrome are ulnar shortening osteotomy and wafer procedure, whether open or arthroscopically, to decompress the ulnocarpal joint load. However, all of these techniques have their shortcomings and drawbacks. The current study demonstrates a novel technique to decompress the ulnocarpal joint load: the "reverse wafer procedure" for ulnar impaction syndrome. In this surgical technique, we resected the proximal ulnar side of the lunate instead of partial resection of the thin wafer of the distal ulnar head dome in the standard wafer procedure. This technique avoids iatrogenic central tear of triangular fibrocartilage and distal radioulnar joint portal arthroscopy, which is technically demanding while preserving the distal radioulnar joint.

Arthroscopic wafer procedure versus ulnar shortening osteotomy for ulnar impaction syndrome: a systematic review and meta-analysis

PURPOSE

This study aimed to systematically compare the efficacy and safety of arthroscopic wafer procedure (AWP) versus ulnar shortening osteotomy (USO) for ulnar impaction syndrome (UIS) treatment.

METHODS

All the studies included in this meta-analysis compared the efficacy of AWP to USO for UIS and were acquired through a comprehensive search across multiple databases. The meta-analysis was performed by calculating the effect sizes with the Cochrane Collaboration's RevMan 5.4 software.

RESULTS

A total of 8 articles were included in this analysis, comprising 148 cases in the AWP group and 163 cases in the USO group. The pooled estimates indicated no significant differences in combined Darrow's Criteria or Modified Mayo Wrist Score, Modified Mayo Wrist Score, DASH scores, grip strength, VAS score, and postoperative ulnar variation. On the other hand, the patients in the AWP group exhibited fewer complications (OR = 0.17, 95%CI 0.05-0.54, P = 0.003) and a lower reoperation rate (OR = 0.12, 95%CI 0.05-0.28, P < 0.00001) than those in the USO group.

CONCLUSIONS

The two surgical techniques were both effective in treating UIS but the AWP group showed fewer complications and a lower reoperation rate. Therefore, AWP may present a superior alternative for UIS treatment.

Results of isolated ulnar shaft shortening osteotomy in the treatment of idiopathic ulnocarpal impaction syndrome

The objective of this study was to evaluate the results of isolated ulnar shaft shortening osteotomy (USSO) in the treatment of idiopathic ulnocarpal impingement syndrome. This was a two-center retrospective study. All patients older than 18 years who underwent isolated USSO for idiopathic ulnocarpal impingement syndrome between 2006 and 2016 were included. The outcome measures were: patient satisfaction, decrease in pain intensity, change in occupation, QuickDASH and PRWE functional scores, secondary palliative surgery suggesting failure of the ulnar shaft shortening osteotomy, and postoperative ulnar variance. The main complications were analyzed. Thirty-one patients were included. Twenty-six (84%) were satisfied with the procedure. At an average follow-up of 62 months, there was no secondary palliative surgery. Mean pain intensity on VAS was 7/10 (range, 2-10) and 1.7/10 (range, 0-6) preoperatively and postoperatively, respectively, for a mean decrease of 5.3 ± 2.6 points; this decrease was statistically significant (p &lt; 0.001). None of the manual workers had to alter their work. Mean postoperative QuickDASH score was 19.6/100 (range, 0-79.55) and mean postoperative PRWE score was 23/100 (range, 1-85). Mean postoperative ulnar variance was -0.5 mm. As for complications, 61% of patients (n = 19/31) had discomfort related to the plate; 9.7% (n = 3/31) had distal radioulnar osteoarthritis; 4% (n = 1/19) had a fracture after hardware removal; 13% (n = 4/31) had non-union. Despite a high rate of complications, the study confirmed the effectiveness, in terms of pain, of isolated USSO in the treatment of idiopathic ulnocarpal impingement syndrome. LEVEL OF EVIDENCE: IV; retrospective cohort.

Ulnar-Side Wrist Pain Management Guidelines: All That Hurts is Not the TFCC!

BACKGROUND

Ulnar-sided wrist pain is a common clinical problem, most often misdiagnosed as triangular fibrocartilage complex (TFCC) injury. It may be frustrating to the patient, as one may end up wearing a wrist splint for an unusually long period, disrupting their routine.

PURPOSE

Because of the dilemmas in the diagnosing the cause of ulnar-sided wrist pain, various algorithms have been suggested but it is an individual's choice to do a systematic assessment and follow in their routine clinical practice. We propose the 'storey concept' for examining the ulnar side of the wrist, with ulnar styloid as the reference point. The lower storey identifies the pathologies of the DRUJ, the intermediate storey identifies the pathologies of the radiocarpal joint and the upper storey identifies the pathologies of midcarpal and carpometacarpal joint.

CONCLUSION

Also, it is important to ramify the cause of pain into stable or unstable wrist, with or without arthritis, as this will guide us in managing the pain arising from distal radioulnar joint. In addition to methodical clinical examination, ideal radiographs and high-resolution MRI are critical to diagnose wrist pathologies. The role of wrist arthroscopy has consistently increased, and complements in both diagnosis and treatment of wrist pain especially in ambiguous situations.

Loading at the distal radius and ulna during active simulated dart throw motion

Loading at the distal forearm during dart throw motion (DTM) has been examined under static loads but there is no consensus on how loading is affected by active motion. In this work two implants were designed to measure forearm loading in a cadaveric model of wrist motion. Loads through the radius and ulna were significantly greater in reverse DTM than forward DTM. Radius loads were greatest in extended and radial deviated positions, and ulnar loads were greatest in flexed and ulnar deviated position. This work gives insight into the biomechanics of loading of the forearm to guide further studies.

An In Vitro Study to Determine the Effect of Ulnar Shortening on Distal Forearm Loading During Wrist and Forearm Motion: Implications in the Treatment of Ulnocarpal Impaction

PURPOSE

To evaluate the effect of ulnar shortening on distal forearm loading following simulated dynamic motion.

METHODS

Ulnar shortening was simulated using a custom-built adjustable implant to simulate up to 4 mm of ulnar shortening (-4 mm) in 9 cadaveric extremities. Load cells were placed in the distal ulna and radius to quantify axial loading. Using a wrist and forearm motion simulator, absolute and percentage loads were measured during dynamic flexion, ulnar deviation (UD), flexion dart throw (DT), and pronation.

RESULTS

There was a significant decrease in absolute and percentage distal ulnar loads at each interval of ulnar shortening during flexion, UD, DT, and pronation. The distal ulna bore no compressive loads, and in fact, tensile loads were measured in the ulna at 2 mm of ulnar shortening during DT and pronation, at 3 mm during flexion, and at 4 mm during UD.

CONCLUSIONS

A progressive decrease in distal ulnar loads with generation of tensile loads was observed with sequential ulnar shortening.

CLINICAL RELEVANCE

Ulnar shortening greater than 2 mm can result in tensile loading in the distal ulna. When managing ulnar impaction syndrome, excessive shortening may not be required to provide relief of symptoms.

Effect of Radial Lengthening on Distal Forearm Loading Following Simulated In Vitro Radial Shortening During Simulated Dynamic Wrist Motion

PURPOSE

To evaluate the effect of radial length change on distal forearm loading during simulated dynamic wrist motion.

METHODS

A custom-built adjustable radial implant was used to simulate up to 4 mm of distal radius shortening (-4 mm) and 3 mm of lengthening (+3 mm). Load cells were placed in the distal radius and ulna in cadavers to measure their respective axial loads. The specimens were mounted on a wrist motion simulator that produced active wrist motion via tendon actuation. To simulate radial lengthening osteotomy following radial shortening from malunion, the radius was sequentially lengthened by 1-mm intervals from -4 mm to +3 mm. Radial and ulnar loads were measured during simulated wrist flexion, ulnar deviation (UD), and flexion dart throw (DT) at each interval of radial lengthening up to +3 mm.

RESULTS

During wrist flexion and UD, for each millimeter of radial lengthening from -4 mm to the native length, there was a significant increase in distal radial loads. No significant change in radial load was observed beyond the native length during flexion and UD. There was no change in distal radial loads during DT for each interval of radial lengthening from -4 mm to +3 mm. A sequential decrease in ulnar loads was observed as the radius was lengthened from -4 mm to +3 mm for all wrist motions evaluated.

CONCLUSIONS

Radial lengthening beyond the native length was not detrimental to radial loading and further reduced distal ulnar loading; achieving at least native ulnar variance seems to be appropriate to restore normal biomechanical loading based on this in vitro study.

CLINICAL RELEVANCE

Lengthening of the radius beyond native variance in the setting of ulnar impaction syndrome, distal radius malunion, or distal radioulnar instability may not result in excessive loading of the distal radius and further reduces loading on the distal ulna. Surgeons should obtain contralateral wrist x-rays to serve as a template when performing distal radius osteotomies.

Arthroscopic Management of Ulnocarpal Impaction Syndrome and Ulnar Styloid Impaction Syndrome

Both ulnocarpal impaction syndrome and ulnar styloid impaction syndrome can produce ulnar wrist pain. The definition and clinical differentiation are explained. The relevant anatomy, biomechanics, causes, diagnosis, and arthroscopic treatments, as well as the surgical indications, techniques, and outcomes of these syndromes are discussed in detail.

The Oblique Metaphyseal Shortening Osteotomy of the Distal Ulna: Surgical Technique and Results of Ten Patients

Background Ulnocarpal abutment is a common condition following distal radius fractures. There are different surgical methods of treatment for this pathology: open and arthroscopic wafer procedure or an ulnar shortening osteotomy. We describe an oblique metaphyseal shortening osteotomy of the distal ulna using two cannulated headless compression screws. We report the results of 10 patients treated with this method. Materials and Methods Out of 17 patients, 10 could be reviewed retrospectively for this study. Patient-rated outcomes were measured using the VAS (visual analogue scale) for pain, PRWHE (patient-rated wrist and hand evaluation) survey, and Quick-DASH (disability of arm, shoulder and hand) survey for functional outcomes. At the review we measured the range of motion (ROM) of the wrist (extension and flexion, ulnar and radial deviation, pronation and supination). Grip strength, pronation, and supination strength of the forearm was measured using a calibrated hydraulic dynamometer. ROM and strength of the affected wrist was compared with ROM and strength of the unaffected wrist. Surgical Procedure Oblique long metaphyseal osteotomy of the distal ulna (from proximal-ulnar to distal-radial), fixed with two cannulated headless compression screws. Results The average postoperative VAS score for pain was 23.71 (standard deviation [SD] of 30.41). The average postoperative PRWHE score was 32.55 (SD of 26.28). The average postoperative Quick-DASH score was 28.65 (SD of 27.21). The majority of patients had a comparable ROM and strength between the operated side and the non-operated side. Conclusion This surgical technique has the advantage of reducing the amount of hardware and to decrease the potential hinder caused by it on medium term. Moreover, the incision remains smaller, and the anatomic metaphyseal localization of the osteotomy potentially allows a better and rapid healing.

Distal Radioulnar Joint Reaction Force Following Ulnar Shortening: Diaphyseal Osteotomy Versus Wafer Resection

PURPOSE

To compare how ulnar diaphyseal shortening and wafer resection affect distal radioulnar joint (DRUJ) joint reaction force (JRF) using a nondestructive method of measurement. Our hypothesis was that ulnar shortening osteotomy would increase DRUJ JRF more than wafer resection.

METHODS

Eight fresh-frozen human cadaveric upper limbs were obtained. Under fluoroscopic guidance, a threaded pin was inserted into the lateral radius orthogonal to the DRUJ and a second pin was placed in the medial ulna coaxial to the radial pin. Each limb was mounted onto a mechanical tensile testing machine and a distracting force was applied across the DRUJ while force and displacement were simultaneously measured. Data sets were entered into a computer and a polynomial was generated and solved to determine the JRF. This process was repeated after ulnar diaphyseal osteotomy, ulnar re-lengthening, and ulnar wafer resection. The JRF was compared among the 4 conditions.

RESULTS

Average baseline DRUJ JRF for the 8 arms increased significantly after diaphyseal ulnar shortening osteotomy (7.2 vs 10.3 N). Average JRF after re-lengthening the ulna and wafer resection was 6.9 and 6.7 N, respectively. There were no differences in JRF among baseline, re-lengthened, and wafer resection conditions.

CONCLUSIONS

Distal radioulnar joint JRF increased significantly after ulnar diaphyseal shortening osteotomy and did not increase after ulnar wafer resection.

CLINICAL RELEVANCE

Diaphyseal ulnar shortening osteotomy increases DRUJ JRF, which may lead to DRUJ arthrosis.

Force variations in the distal radius and ulna: effect of ulnar variance and forearm motion

PURPOSE

To better define normal wrist joint forces during wrist motion and forearm motion at specific wrist and forearm positions and to see if there is a relationship between these forces and the amount of ulnar variance. A secondary purpose was to determine the relationship between the thickness of the articular disk of the triangular fibrocartilage complex and the amount of force transmitted through the distal ulna.

METHODS

Multi-axis load cells were attached to the distal radius and ulna of 9 fresh cadaver forearms. The axial radial and ulnar compressive forces were recorded while each wrist was moved through wrist and forearm motions using a modified wrist joint simulator. During each motion, the tendon forces required to cause each motion were recorded. The ulnar variance and triangular fibrocartilage complex articular disc thickness were measured.

RESULTS

The axial force through the distal ulna and the wrist extensor forces were greatest with the forearm in pronation. No relationship was found between the amount of force through the distal ulna and the amount of ulnar variance. A strong inverse relationship was found between the triangular fibrocartilage complex thickness and the ulnar variance.

CONCLUSIONS

Wrists with positive ulnar variance have generally been thought to transmit greater loads across the distal ulna, which has been felt to predispose these wrists to the development of ulnar impaction. The results of this study appear to show that all wrists have similar loading across the distal ulna regardless of ulnar variance. By comparison, pronation relatively increases loading across the distal ulna.

CLINICAL RELEVANCE

Because these results suggest that within reasonable ranges of ulnar variance loading across the distal ulna is independent of ulnar variance, the clinically observed incidence of ulnar impaction is more likely the result of increased wear on a thinner and less durable triangular fibrocartilage complex than due to increased distal ulna loading in ulnar positive variant wrists.

Ulnar shortening osteotomy for distal radius malunion

Background Malunion is a common complication of distal radius fractures. Ulnar shortening osteotomy (USO) may be an effective treatment for distal radius malunion when appropriate indications are observed. Methods The use of USO for treatment of distal radius fracture malunion is described for older patients (typically patients >50 years) with dorsal or volar tilt less than 20 degrees and no carpal malalignment or intercarpal or distal radioulnar joint (DRUJ) arthritis. Description of Technique Preoperative radiographs are examined to ensure there are no contraindications to ulnar shortening osteotomy. The neutral posteroanterior (PA) radiograph is used to measure ulnar variance and to estimate the amount of ulnar shortening required. An ulnar, mid-sagittal incision is used and the dorsal sensory branch of the ulnar nerve is preserved. An USO-specific plating system with cutting jig is used to create parallel oblique osteotomies to facilitate shortening. Intraoperative fluoroscopy and clinical range of motion are checked to ensure adequate shortening and congruous reduction of the ulnar head within the sigmoid notch. Results Previous outcomes evaluation of USO has demonstrated improvement in functional activities, including average flexion-extension and pronosupination motions, and patient reported outcomes. Conclusion The concept and technique of USO are reviewed for the treatment of distal radius malunion when specific indications are observed. Careful attention to detail related to surgical indications and to surgical technique typically will improve range of motion, pain scores, and patient-reported outcomes and will reduce the inherent risks of the procedure, such as ulnar nonunion or the symptoms related to unrecognized joint arthritis.

LEVEL OF EVIDENCE

 Level IV.

Distal metaphyseal ulnar shortening osteotomy: technique, pearls, and outcomes

Background Ulnar sided wrist pain is a commonly encountered complaint of the hand surgeon, and ulnar impaction is a common cause. Surgical treatment aims to reduce the force transmitted through the ulna and traditionally includes diaphyseal ulnar shortening osteotomy and the "wafer" procedure. These procedures have known shortcomings. We describe an alternative option known as the distal metaphyseal ulnar shortening osteotomy (DMUSO). Materials and Methods Retrospective review of eight procedures was undertaken to assess radiographic healing, objective measurements of wrist and forearm motion, grip and pinch strength, and subjective measures of Disabilities of the Arm, Shoulder, and Hand (DASH), Patient-Rated Wrist Evaluation (PRWE), and Michigan Hand Outcomes Questionnaire (MHQ) at a minimum of 12 months following surgery. Description of Technique A wedge osteotomy is made in the osteochondral region of the distal metaphysis of the ulna, and a headless compression screw is used for fixation. Results Five women and three men underwent DMUSO with average follow up at 13 months; the dominant wrist was affected in 7 of 8 patients. The affected wrist had less motion in all planes, and grip and pinch strength was also less in the affected wrist, but only wrist extension was significantly different from the contralateral side. These findings likely did not have an effect on the clinical outcome. Subjective outcomes included average DASH score of 13 (0-35), PRWE 19 (40-11), and MHQ score of 88 (85-100). Conclusions DMUSO is a viable option for patients with ulnar impaction syndrome. It requires intra-articular exposure of the distal radioulnar joint (DRUJ) but is less invasive then diaphyseal shortening. It permits early and reliable return of joint motion and function while avoiding the potential need for hardware removal by using a buried screw.

Ulnar Impaction Syndrome: Ulnar Shortening vs. Arthroscopic Wafer Procedure

The outcome of ulnar shortenings was compared with that of arthroscopic wafer resections for ulnar impaction (or abutment) syndrome in patients with a positive ulnar variance. The outcome was measured by DASH score, visual analog scale for pain, and working incapacity. The mean DASH score in the ulnar shortening group was 26; in the wafer group it was 36. The VAS scores were respectively 4.4 and 4.6. The working incapacity was 7?months in the ulnar shortening group and 6.1 months in the wafer group. The differences between the two groups were not statistically significant.

Ulnar impaction

Ulnar impaction syndrome is a common source of ulnar-sided wrist pain. It is a degenerative condition that occurs secondary to excessive load across the ulnocarpal joint, resulting in a spectrum of pathologic changes and symptoms. It may occur in any wrist but is usually associated with positive ulnar variance, whether congenital or acquired. The diagnosis of ulnar impaction syndrome is made by clinical examination and is supported by radiographic studies. Surgery is indicated if nonoperative treatment fails. Although a number of alternatives exist, the 2 primary surgical options are ulnar-shortening osteotomy or partial resection of the distal dome of the ulna (wafer procedure). This article discusses the etiology of ulnar impaction syndrome, and its diagnosis and treatment.

Reconstruction of the distal ulna: instability, impaction, impingement, and arthrosis

A number of afflictions may affect the distal radioulnar joint that can lead to severe pain, disuse, dysfunction, and disability. The disorders that affect this small anatomic region are complex, have multifactorial etiologies, and can sometimes present difficult diagnostic and treatment options. This article presents an overview of recent developments in the diagnosis and treatment of a variety of conditions that affect the joint and surrounding bone and soft tissues.

Arthroscopic treatment of ulnar impaction syndrome

Ulnar impaction syndrome occurs in the setting of a central traumatic or degenerative defect in the triangular fibrocartilage complex in patients with ulnar positive variance. Chondral and subchondral edema, mechanical impingement of the articular disc, and chondromalacia of the distal ulna, proximal lunate, and proximal triquetrum produce symptoms with activity that do not improve with rest. Decreasing ulnocarpal load-sharing across the wrist with recession of the distal ulna is necessary to relieve symptoms in the majority of patients. Arthroscopic treatment with triangular fibrocartilage complex debridement and arthroscopic ulnar wafer resection is an effective treatment for ulnar impaction syndrome. It affords a single-stage, minimally invasive approach, with similar efficacy and fewer complications than open wafer resection or ulnar shortening osteotomy.

Current concepts in wrist arthroscopy

The purpose of this article is to review the recent literature on arthroscopic treatment of distal radius fractures (DRFs), triangular fibrocartilage complex injuries, intercarpal ligament injuries, and ganglion cysts, including the use of electrothermal devices. A major advantage of arthroscopy in the treatment of DRFs is the accurate assessment of the status of the articular surfaces and the detection of concomitant injuries. Nonrandomized studies of arthroscopically assisted reduction of DRFs show satisfactory results, but there is only 1 prospective randomized study showing the benefits of arthroscopy compared with open reduction-internal fixation. Wrist arthroscopy plays an important role as part of the treatment for DRFs; however, the treatment for each practitioner and each patient needs to be individualized. Wrist arthroscopy is the gold standard in the diagnosis and treatment of triangular fibrocartilage complex injuries. Type 1A injuries may be successfully treated with debridement, whereas the repair of type 1B, 1C, and 1D injuries gives satisfactory results. For type 2 injuries, the arthroscopic wafer procedure is equally effective as ulnar shortening osteotomy but is associated with fewer complications in the ulnar positive wrist. With interosseous ligament injuries, arthroscopic visualization provides critical diagnostic value. Debridement and pinning in the acute setting of complete ligament tears are promising and proven. In the chronic patient, arthroscopy can guide reconstructive options based on cartilage integrity. The preliminary results of wrist arthroscopy using electrothermal devices are encouraging; however, complications have been reported, and therefore, their use is controversial. In dorsal wrist ganglia, arthroscopy has shown excellent results, a lower rate of recurrence, and no incidence of scapholunate interosseous ligament instability compared with open ganglionectomy. Arthroscopy in the treatment of volar wrist ganglia has yielded encouraging preliminary results; however, further studies are warranted to evaluate the safety and efficacy of arthroscopy.

Cartilage-retaining wafer resection osteotomy of the distal ulna

Ulnar-sided wrist pain resulting from ulnar impaction is common. We describe a new cartilage-retaining wafer resection osteotomy designed to keep the cartilage intact and decompress the ulnocarpal articulation without requiring internal fixation. We retrospectively reviewed seven patients with ulnar impaction who had the procedure. The minimum followup was 14 months (mean, 30 months; range, 14-38 months). The mean change in ulnar variance was -1.29 mm. Patients showed radiographic healing by a mean of 11 weeks. Our preliminary results suggest the cartilage-retaining wafer resection osteotomy may be an effective way to unload the ulnocarpal joint without requiring internal fixation or destruction of the distal ulna cartilage.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Osteoarthritis of the wrist

Osteoarthritis of the wrist is one of the most common conditions encountered by hand surgeons. It may result from a nonunited or malunited fracture of the scaphoid or distal radius; disruption of the intercarpal, radiocarpal, radioulnar, or ulnocarpal ligaments; avascular necrosis of the carpus; or a developmental abnormality. Whatever the cause, subsequent abnormal joint loading produces a spectrum of symptoms, from mild swelling to considerable pain and limitations of motion as the involved joints degenerate. A meticulous clinical and radiographic evaluation is required so that the pain-generating articulation(s) can be identified and eliminated. This article reviews common causes of wrist osteoarthritis and their surgical treatment alternatives.

[The step-cut shortening osteotomy of the shaft of the ulna, technique and results]

Step-cut shortening osteotomy of the ulna for impingment of the distal ulna relies on the principles enunciated by Desanfans 1953. We recommend the plate be placed on either the palmar or the dorsal aspect of the ulna. Used since 1990 this technique has enabled primarily bony healing by 6 months in all the 18 cases operated upon. A significant clinical improvement as measured by the scoring system of Chun and Palmer was noted at a median follow-up of 95.7 months. Shortening did not unfortunately, appear to stabilize the distal ulna and those patients with residual clinical radioulnar instability had significantly worse results. We conclude that the technique presented gives reliable bone healing. It is a versatile and simple technique that requires no special instrumentation but does demand skill and precision.

The effect of radial shortening on wrist joint mechanics in cadaver specimens with inherent differences in ulnar variance

PURPOSE

To assess load changes in the wrist and forearm resulting from surgically-induced radial shortening in wrists with inherent differences in ulnar variance.

METHODS

Eleven fresh cadaver upper extremities, 4 with ulnar-plus variance of 2 mm or greater and 7 with ulnar-minus variance of 2 mm or greater were used. The radius and ulna of each specimen were instrumented with load cells, a 15-mm segment of the radius was resected and replaced with aluminum blocks of various sizes, and the specimens were loaded with 143 N (32 lb) at 1-mm differences of radial length. The load distribution between the radius and ulna was measured.

RESULTS

The load distribution in the specimens with an ulnar-plus variance averaged 69% through the radius and 31% through the ulna. In the wrists with ulnar-minus variance, the load distribution averaged 94% through the radius and 6% through the ulna. The mean force in the ulna increased and the mean force in the radius decreased with incremental shortening of the distal end of the radius. The mean force through the ulna in the ulnar-plus-variance group was always higher than that of the ulnar-minus-variance group. When compared not by the number of millimeters of radial shortening but by the adjusted ulnar variance, there was no difference between the ulnar-plus-variance and the ulnar-minus-variance groups.

CONCLUSIONS

Wrists with ulnar-minus variance could accommodate radial shortening without as much increase in the ulna load as wrists with ulnar-plus variance. The clinical relevance is that a patient with an ulnar-minus variance may accommodate more radial shortening after a wrist fracture without developing an ulnar impaction syndrome than a patient with an ulnar-plus-variant wrist.

Ulnar impaction syndrome

Although Palmer's classification of TFCC lesions differentiates post-traumatic central perforations (IA tears) from degenerative tears secondary to ulnocarpal impaction (IIC) [3], the distinction is not always clear clinically. In the final analysis, the literature suggests that as many as 25% of wrists with TFCC tears have residual symptoms following arthroscopic debridement alone [23], and it is likely that static or dynamic ul-nar positive variance plays a role [2,5,17,25]. The authors' results suggest that combined arthroscopic TFCC debridement and wafer resection are feasible and efficacious as treatment for all stages of ulnar impaction syndrome. When class II A and B changes are observed, that is, when a TFCC perforation has not yet developed, the authors have observed favorable results in most patients following arthroscopic TFCC central disc excision and wafer resection as an alternative to ulnar shortening osteotomy [33] or open wafer excision [10].