Long-Term Results of Arthroscopic Capsular Shrinkage for Palmar Midcarpal Instability of the Wrist

Abstract

Background  Midcarpal instability is a term for a collection of poorly understood conditions where the proximal row of the carpus is unstable. The most common type of midcarpal instability is palmar midcarpal instability (PMCI). Treatment for PMCI includes nonoperative proprioceptive retraining of the wrist, splints, and strengthening. If this fails, various authors have suggested several different fusions, tenodesis procedures, or capsular shrinkage. There are no long-term case series in the literature.

Objective  The aim of this study is to assess the long-term results of arthroscopic capsular shrinkage when used for PMCI of the wrist.

Methods  A prospective cohort study of patients who underwent arthroscopic capsular shrinkage for PMCI was performed. Ethical board approval was given for this study. All patients were followed up and reviewed independently from the operating surgeon. Assessment included a structured questionnaire, disabilities of the arm, shoulder and hand (DASH) questionnaire, and clinical examination using a goniometer. PMCI was assessed objectively with the anterior drawer test and radiological imaging was only performed if clinically relevant to the residual symptoms.

Results  Thirteen patients (15 wrists) underwent arthroscopic capsular shrinkage for PMCI. Twelve patients (14 wrists) were available for clinical review with a follow-up rate of 92.3%. The mean time from index procedure to final review was 12 years (range: 10–14years). The symptoms of instability had completely resolved in nine wrists (7 patients). Only 2 of the 14 wrists had symptoms that were reproduced with a positive anterior drawer test. All other wrists were stable on objective assessment. The mean DASH score had improved from pre op of 34 to post op of 12.1 and at 12-year follow-up this had deteriorated minimally to 15.3. Assessment of the range of motion showed an average increase in range of flexion/extension by 22 degrees. Patient satisfaction was excellent. The patients rated that nine wrists were much better than presurgery, three as better, one unchanged, and one worse.

Discussion/Conclusion  There are no studies looking at the long-term natural history of treatments for PMCI. The lead author proposes a grading system for symptomatic PMCI that has been retrospectively applied to this cohort. It is a grading system from 1 to 4 and is based on a treatment algorithm. This is the first long-term study from any joint, where the results of capsular shrinkage have been maintained over time. In this series, we have not seen any deleterious effect from possible mechanoreceptor injury. We suspect that functioning mechanoreceptors are more relevant in the unstable joint, than the structurally stable joint. The authors propose that thermal capsular shrinkage is an effective and durable option for use in mild-to-moderate forms of PMCI.

Midcarpal instability (MCI) is a term for a collection of poorly understood conditions where the proximal row of the carpus is unstable. ^{1 2} It is classified as a nondissociative type of carpal instability. ^{1 3} The most common type of MCI is palmar midcarpal instability (PMCI), although this is still rarely seen in clinical practice. ^{4 5 6} The ulnar side of the proximal row has a tendency to tilt in a palmar direction when under tension and in radial deviation. ⁷ As the wrist ulnar deviates, the proximal row extends, but in PMCI, ligament laxity prevents the smooth transition and instead the proximal row extends suddenly. This is known as the “catch up clunk.” ¹ Patients present with pain and giving way of the wrist. The giving way occurs when the wrist is in the pronated position as it thought that the pathophysiology is particularly due to laxity of the ulnar arm of palmar arcuate ligament (ulnocapitate ligament). ¹

The treatment for dynamic PMCI has included nonoperative proprioceptive retraining of the wrist, ulnar splints, and general strengthening. ¹ If this fails, various authors have suggested several different tenodesis and fusion procedures. ^{1 8 9 10 11} All of these studies have included small numbers of patients with short follow-up. Arthroscopic capsular shrinkage in the shoulder has shown disappointing long-term results with a tendency for instability to recur. ¹² There are no good long-term results of capsular shrinkage in any joint. Capsular shrinkage has been used in the wrist previously for direct treatment of the scapholunate ligament, but only with short-term results being published. ^{13 14} As PMCI is due to ligament laxity of the wrist, Mason and Hargreaves proposed the use of thermal capsular shrinkage to improve the stability. ¹⁵ Long-term results for capsular shrinkage in the treatment of PMCI have not been previously published.

The aim of this study is to assess whether the results of arthroscopic capsular shrinkage deteriorate over the long-term when used for PMCI of the wrist.

Methods

A case series of 13 patients (15 wrists) underwent arthroscopic capsular shrinkage for PMCI. The arthroscopic thermal capsular shrinkage technique for PMCI used by the authors in this patient series has already been described and published. ¹⁶ Using a spotting technique, the thermal probe was activated for 1 second intervals. It is then transferred to another site prior to reactivation. Five sites were treated on the volar tissues and two sites on the dorsal tissues. Portals were sutured and the wrist was immobilized in either a removable splint or a cast for a 6-week period of time following the surgery. All patients were prospectively followed up. Preoperatively, the patients were examined and diagnosed with PMCI by reproducing their symptoms by performing the ulnar shift test and palmar midcarpal drawer test. A patient had a positive result if a clunk and pain was produced during the clinical examination. We have reviewed this group at more than 10 years following their index procedure. The demographics, procedure, and early results have been previously published. ¹⁵ Ethical board approval was given for this study and all patients were reviewed independently from the operating surgeon to decrease bias. Clinical assessment included a structured questionnaire including four specific instability questions ( Table 1 ). ¹⁵ This created an instability score with four being the least (no instability) and 20 for the maximum degree of instability. Subjective functional assessment was performed with a DASH questionnaire. ¹⁷ Clinical examination included a range of motion that was measured with a goniometer on the dorsum of the wrist. PMCI was specifically assessed objectively with the anterior drawer test. ¹⁸ Radiological imaging was only performed if clinically relevant to the residual symptoms. Hargreaves proposed a grading system for symptomatic PMCI that is shown in Table 2 . ⁴

Table 1. A structured questionnaire used to assess subjective outcome.

Please ring the most appropriate response
	Before surgery	Now
Does your wrist clunk or give way?	Never Rarely Sometimes Often	Never Rarely Sometimes Often
When you try to pour a fairly heavy kettle, does your wrist clunk?	Never Rarely Sometimes Often Always	Never Rarely Sometimes Often Always
When you try to pour a fairly heavy kettle, does your wrist give way?	Never Rarely Sometimes Often Always	Never Rarely Sometimes Often Always
When you try to pour a fairly heavy kettle, is it painful?	Never Rarely Sometimes Often Always	Never Rarely Sometimes Often Always
Have you returned to work since the operation?	Yes—same Yes—different No
When did you go back to work?	Weeks/months
Remembering how you were before the operation, would you say that your main problem in the wrist is now much better, unchanged or worse?	Much better Better Unchanged Worse
Remembering how you were before the operation would you have the operation again?	Yes No

Table 2. The Hargreaves grading system for PMCI.

		Description	Surgical treatment options
Grade 0	Presymptomatic	No symptoms of instability but able to perform voluntary catch up clunk. Patient at risk of symptoms	No treatment
Grade 1	Dynamic	Symptoms of giving way. Symptoms reproduced with a positive midcarpal shift test. No voluntary clunk or sag	Soft tissue stabilization or arthroscopic capsular shrinkage
Grade 2	Voluntary dynamic	Symptomatic giving way with voluntary subluxation (ulnar sag sign or voluntarily performed catch up clunk)	Soft tissue stabilization or arthroscopic capsular shrinkage
Grade 3	Static reducible	VISI deformity on lateral X-ray at rest. Deformity easily reducible on manipulation.	Soft tissue stabilization or bone procedure
Grade 4	Static irreducible	Fixed VISI deformity on lateral X-ray. Not easily reducible. Locked	Bone procedure

Abbreviations: PMCI, palmar midcarpal instability; VISI, volar intercalated segment instability.

Results

One patient of the original case series had emigrated and was no longer available for review. Twelve patients (14 wrists) were available for clinical review and follow-up. The mean age of the patients was 38 years with a range of 27 to 58. This corresponds to a follow-up rate of 92.3% from the original series. The mean time from index procedure to final review was 12 years (range: 10–14 years). The patients all suffered with wrist pain with an average duration of 5 years prior to treatment. None of the patients had undergone a prior operative procedure before capsular shrinkage was performed.

The symptoms of instability had been completely resolved in nine wrists (7 patients). In these, there had been no deterioration in function or stability. One patient had excellent correction of symptoms initially, but had started to have a recurrence of mild symptoms at 7 years postsurgery. This corresponds to 71% good or excellent results with four patients having a poor result. One patient had undergone further surgery for PMCI at another center. She had undergone a soft tissue tenodesis, but her instability symptoms continued despite this and has subsequently been diagnosed with multiple sclerosis. No other patients had undergone any other surgical procedure. The poor results were attributed to the coexisting conditions including De Quervain tenosynovitis, flexor sheath ganglion, STT degeneration, and type 3 Ehlers–Danlos syndrome. Only 2 of the 14 wrists had symptoms that were reproduced with a positive anterior drawer test ( Fig. 1 ). All other wrists were stable on objective clinical examination. According to the Hargreaves classification, all cases in this series were graded as either stage 1 or 2. ⁴

Fig. 1.

The number of patients at a mean follow-up of 12 years (range: 10–14 years) with a positive symptomatic draw test on clinical examination.

The mean DASH score of the 12 patients had improved following the initial surgery from 34 to 12.1 ( Fig. 2 ). At 12 years follow-up, this had deteriorated minimally to 15.3. Assessment of the range of motion showed a slight stretching out of the joint with time and the average range of flexion /extension was increased by 22 degrees. The arc of radial and ulnar deviation was also increased by 22% over the past 7 years. Patient satisfaction was excellent with nine wrists rated as much better than pre-surgery, three as better, one unchanged, and one worse. All patients were satisfied with the procedure and would recommend it to others irrespective of their personal final outcome.

Fig. 2.

The mean disabilities of the arm, shoulder and hand (DASH) score preoperatively at a mean follow-up of 42 months (range: 14–67 months) and at a mean follow-up of 144 months (range: 120–168 months).

Discussion

PMCI is the main cause for clunking of the unstable wrist. It often presents with pain and a feeling of giving way or vulnerability. There are no studies looking at the long-term natural history of this condition. Our experience is that ∼50% of patients can be improved with proprioceptive retraining through physiotherapy, but very few spontaneously improve. Within this presented case series are patients who have had symptoms for many years, until treatment was offered. It is evident that there is a requirement for interventional treatments for this condition. Harwood and Turner recently reviewed the nonoperative management of this condition highlighting the low level of evidence available in the literature for conservative management. ¹⁹

This has been retrospectively applied to this group. Currently, the surgical options for mild or moderate (Hargreaves stage 1 and 2) include soft tissue stabilization with a tenodesis, tendon transfer, or arthroscopic capsular shrinkage. Bone procedures, such as radiolunate fusion, are necessary when there is a static volar collapse (Hargreaves Grade 3 and 4). There are no comparative studies in the literature to suggest the best soft tissue option. ^{1 10 11} The current literature is only able to offer short-term results of small case series. The limitations of this study are the lack of grip strength analysis and X-rays from recent follow-up. The absence of an up to date radiograph does make it difficult to assess the development of wrist arthrosis over time.

The arthroscopic management of PMCI using thermal capsular shrinkage has been suggested as an option by several authors. Pathak and Bain presented four cases of multidirectional wrist instability, which were treated with thermal shrinkage and are the only other documented series. ²⁰ Due to the experience of capsular shrinkage in the shoulder, ¹² there has been concern that the results of this series would deteriorate over time and symptoms would recur. The cases, which did well initially from this procedure, seem to have continued to be symptom free with only a late recurrence rate of 10%. This is the first long-term study from any joint, where the results of capsular shrinkage have been maintained over time. It is probable that immobilization of the wrist for 6 weeks postoperatively is important in preventing early stretching of the collagen contraction. Difficulty in immobilizing the shoulder, for as long as 6 weeks, may be a factor that causes the recurrence in that specific joint. Inadvertent thermal injuries to neighboring structures did not occur in this series, but care must be taken to avoid these by using a precautionary technique. More recently, temperature-sensitive probes have been made available, but were not used in this series.

This level 4 case series study has the obvious disadvantage of including a small number, but PMCI is a rare condition. It is, therefore, difficult to gain enough patients for such studies to be performed. To allow corroboration of results, further series of capsular shrinkage from other centers are also required. Hagert et al have suggested that the thermal injury to the capsule will also necrose the adjacent mechanoreceptors. ²¹ These mechanoreceptors are identified as important in the proprioceptive reflexes that help to control the unstable joint. ²² In this series, we have not seen any deleterious effect from possible mechanoreceptor injury and we suspect that the functioning mechanoreceptors are more relevant in the unstable joint than the structurally stable joint.

Conclusion

The authors propose that thermal capsular shrinkage is an effective and durable treatment option for mild-to-moderate PMCI and have demonstrated an improved patient satisfaction in long-term follow-up of 12 years.