Prosthetic Management of Posttraumatic Deformity

Ariane Gerber

Jon J. P. Warner

INTRODUCTION

Posttraumatic deformities of the proximal humerus are rare conditions that occur after neglected or conservatively treated displaced fractures or complications after surgical treatment. In addition to skeletal deformity, osteonecrosis, poor bone quality, bone loss, soft-tissue damage and nerve injury may be present, adding to the complexity in the treatment of those conditions (Table 13-1).

Only a few reports are available in the literature regarding indications and treatment of posttraumatic deformity after proximal humerus fractures. Indication for both reconstruction with corrective osteotomy and replacement arthroplasty remains controversial because functional gain and prognosis are often unpredictable. Nevertheless, careful consideration of the patient’s history—and examination and accurate radiographic analysis—may increase accuracy of future classifications, allowing the surgeon to select the most appropriate therapeutic modality.

This chapter provides a general treatment algorithm for these clinically and surgically challenging situations and focuses on surgical technique of replacement arthroplasty.

SURGICAL ANATOMY

Normal Anatomy

The variability of proximal humeral anatomy in terms of head diameter, head inclination, head retroversion, and head offsets has been shown previously in several cadaveric studies (1, 2, 3). Restoration of anatomy is considered to be the key principle of modern shoulder arthroplasty and is believed to be a requirement to restore function after reconstruction (4,5). Although nearly anatomic reconstruction is technically feasible in simple osteoarthritis of the glenohumeral joint with third-generation implants (6), the irreversible loss of anatomic landmarks in many posttraumatic deformities renders replacement arthroplasty a difficult task. In those cases, reconstruction is always an approximation of the original anatomy and may explain, to some extent, the unpredictable recovery of function observed in this group of patients. Indeed, this observation is supported by published data (7) showing that the outcome of replacement arthroplasty for posttraumatic deformities is poor in the presence of severe skeletal deformity. On the other hand, the natural history of posttraumatic conditions such as avascular necrosis has been shown to be favorable in terms of pain and function provided the anatomy of the proximal metaphyseal humerus (tuberosity to head relationship) has been restored (8).

The Greater Tuberosity: A Key Element for Reconstruction

The importance of the greater tuberosity in malunion and nonunion as an anatomic landmark has been recognized previously. Neer was the first to emphasize the relevance of optimal management of greater tuberosity malpositioning (4). In replacement arthroplasty for malunion, he recommended to accept some malpositioning of the implant to avoid greater tuberosity osteotomy, which, in his experience, led to poor functional outcome. This has been confirmed by others (9,10).

We believe that if a prosthesis can be adapted to the distorted anatomy without compromising the original humeral head size and without osteotomy of the greater tuberosity, the position of the greater tuberosity in relationship to the humeral shaft and to the original head may be accepted. In other words, the three-dimensional orientation of the greater tuberosity would be accepted as an approximation of normal anatomy, and this would be a better compromise than osteotomy and refixation. Conversely, if the position of the greater tuberosity is defined and is considered anatomic, then the so-called lateral column of the proximal humerus is reconstituted and the position of the humeral head can be determined in terms of height and retroversion (Fig. 13-1).

Figure 13-1 The greater tuberosity as a key element for reconstruction. If the position of the greater tuberosity is anatomic, then the position of the humeral can be determined in regard of retroversion and inclination. A: anterior view. B: posterior view. C: axillary view.

TABLE 13-1 POSTTRAUMATIC DEFORMITIES OF THE PROXIMAL HUMERUS

	Level of Deformity	Deformities	Preferred treatment	Functional Outcome
A. Simple Deformities	1. TUBEROSITY	Lesser tuberosity malunion/nonunion Greater tuberosity malunion/nonunion	Joint preserving reconstruction Joint preserving reconstruction	Predictable and good
	2. SURGICAL NECK	Surgical neck malunion Surgical neck nonunion	Joint preserving reconstruction Joint preserving reconstruction
	3. HUMERAL HEAD	Head Impression < 50% of articular surface > 50% of articular surface Avascular necrosis Head split	Joint preserving reconstruction Anatomical replacement arthroplasty Anatomical replacement arthroplasty Anatomical replacement arthroplasty
B. Adaptable Deformities	1. TUBEROSITY AND HEAD	Chronic valgus impacted 4-part fracture	Adapted replacement arthroplasty	Predictable and satisfactory
	2. SURGICAL NECK AND HEAD	Surgical neck malunion and head deformity	Adapted replacement arthroplasy
	3. COMPLEX SKELETAL DEFORMITIES	Malunited minimally displaced three- or four part fractures	Adapted replacement arthroplasy
C. Complex Deformities	1. COMPLEX SKELETAL DEFORMITIES	Complex non-adaptable skeletal deformities Surgical neck nonunion with extensive head cavitation or collapse	Fracture like arthroplasty or reversed arthroplasty Fracture like arthroplasty or reversed arthroplasty	Unpredictable and poor
	2. ANY SKELETAL DEFORMITY WITH FATTY DEGENERATION AND ATROPHY OF THE ROTATOR CUFF	Simple, adaptable skeletal deformities and loss of subscapularis function Simple, adaptable skeletal deformities and loss of supraspinatus and infraspinatus function Complex skeletal deformity and loss of any portion of the rotator cuff	Adapted replacement arthroplasty combined with pectoralis major transfer Adapted replacement arthroplasty or reversed arthroplasty Adapted replacement arthroplasty or reversed arthroplasty
	3. ANY SKELETAL DEFORMITY WITH IRREVERSIBLE DELTOID DYSFUNCTION	Simple, adaptable skeletal deformity Complex skeletal deformities	Adapted replacement arthroplasty or fusion Fusion

Pathoanatomy

Pathoanatomy of deformities represents a complex range of bony and soft-tissue distortion. Therefore, to analyze the numerous posttraumatic conditions, the following levels of deformity should be considered: (a) tuberosity, (b) surgical neck, (c) humeral head, and (d) soft-tissue deformity (atrophy and fatty degeneration of the rotator cuff, irreversible loss of function of the deltoid muscle).

Depending on the number of levels involved, posttraumatic deformities can be divided into three main categories: (A) Simple deformities involving only one level of deformity and characterized through predictable and good functional outcome with established, mostly joint preserving surgical treatment; (B) Adaptable deformities constitute a group of malunion with two or more levels of deformity associated with joint incongruity. However, the degree of deformity still allows treatment with conventional replacement arthroplasty without osteotomy of the greater tuberosity. In this category acceptable functional outcome can be expected. (C) Complex deformities involving two or more levels of severe deformity. In these cases the extent of malunion and joint incongruity require replacement arthroplasty with osteotomy of the greater tuberosity. Often, associated proximal humeral malunions may be severe and associated soft-tissue contractures are severe with atrophy of rotator cuff muscles. Outcome after surgical reconstruction in this category is usually fair although unpredictable.

CLASSIFICATION AND TREATMENT ALGORITHM

Simple Deformities

Tuberosity Deformities

Lesser Tuberosity Nonunion/Malunion

Isolated lesser tuberosity fractures are rare. In nonunion or malunion of the lesser tuberosity, the fragment is medialized and may limit internal rotation and require surgical treatment. Osteotomy, mobilization, and refixation in anatomic position is the logical treatment modality, provided the subscapularis muscle is not severely atrophic with fatty degeneration (see “Complex Deformities” later in the chapter). Outcome after osteotomy of isolated lesser tuberosity malunion or nonunion has not been specifically reported in the literature (Fig. 13-2).

Figure 13-2 Isolated lesser tuberosity malunion. A: Preopertive axillary view. B: Preoperative MRI scan showing normal subscapularis muscle. C: Postoperative axillary view.

Greater Tuberosity Nonunion/Malunion

Malunion or nonunion of the greater tuberosity is the result of a secondary displaced or neglected fracture of the greater tuberosity and usually is associated with functional impairment. If treatment is required, osteotomy, mobilization, and refixation are the treatments of choice, in the absence of atrophy and fatty degeneration of the supraspinatus and infraspinatus muscle. It is critical to recognize that chronic displacement of the greater tuberosity may be associated with marked atrophy and fatty replacement of muscle, which results from involution of a non-functioning muscle. This correlates with tissue compliance, and a stiff tendon may be expected in such cases, thus precluding secure repair into the humerus. Fixation technique is not different than in acute fracture. However, capsular contracture must be addressed through open release if present. After healing, good functional results might be expected (11).

Surgical Neck Deformities

Surgical Neck Nonunion

The surgical neck is the most frequent location for nonunion after proximal humerus fracture (12). Surgical neck nonunion usually leads to complete loss of function of the shoulder and is therefore a disabling condition. Longstanding nonunions are associated with poor bone quality of both proximal and distal fragments and shortening of the humerus as a result of bone defect at the level of nonunion. Chronic telescoping of the shaft against the humeral head can lead to cavitation of the humeral head.

Both bone grafting and internal fixation and replacement arthroplasty have been recommended for treatment. Although fixation may be challenging, requiring specific osteosynthesis techniques (Fig. 13-3), high healing rates and spectacular recovery of function have been reported (13, 14).

If the fixation is not possible, the nonunion has to be transformed in four-part fracture through osteotomy of the tuberosities, and reconstruction is then achieved with replacement arthroplasty. From a classification point of view this specific group of surgical neck nonunions has to be considered as Type C deformity because two levels are involved (surgical neck and head) and reconstruction requires osteotomy of the greater tuberosity. Results in such cases are guarded and are very much dependent on the quality of remaining tuberosity and compliance of rotator cuff tendon tissue.

Surgical Neck Malunion

The typical surgical neck malunion most frequently involves a multiplanar deformity which is an extension, internal rotation, and varus deformity. Loss of active flexion and abduction is in direct proportion with anterior and varus angulation (4). This type of deformity may actually cause impingement because change in contour of the proximal humerus can promote outlet impingement. Simple acromioplasty has been reported to alleviate the impingement symptoms (4), and corrective osteotomy of surgical neck deformity greater than 40 degrees has been shown to improve active range of motion significantly (16).

Humeral Head Deformities

Chronic Head Impression Fractures

Head impression fractures occur as a result of an anterior or posterior dislocation. Anterior dislocation leads to a superoposterior head impression fracture (Malgaigne or Hill-Sachs lesion), whereas after traumatic posterior dislocation an anteromedial humeral head defect (McLaughlin lesion) is typical. Large defects (>25% of the articular surface) requiring surgical treatment are almost invariably associated with a locked anterior or posterior dislocation. For some symptomatic patients with humeral head defects greater than 25% of the articular surface, humeral head reconstruction with allograft has been recommended (17). Selection of this joint-preserving technique requires good-quality bone remaining in the humeral head and goodfunctioning rotator cuff. Unfortunately, in chronic, longstanding cases there is disuse osteopenia, which causes the remaining humeral head to be at risk of collapse if this method of treatment is used. In such cases, arthroplasty is indicated. In addition, if the humeral head defect is greater than 50% and/or if glenohumeral arthritis is already present, replacement arthroplasty is the treatment of choice (18).

Posttraumatic Avascular Necrosis

Posttraumatic avascular necrosis without associated tuberosity malunion is relatively well tolerated (8). In advanced cases with symptomatic loss of joint conformity or secondary degenerative changes, replacement arthroplasty is the treatment of choice and leads to good functional results (19,20).

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