PERIPROSTHETIC FRACTURES ABOUT THE ELBOW

PERIPROSTHETIC FRACTURES AFTER MAJOR JOINT REPLACEMENT 0030-5898/99 $8.00 + .OO

PERIPROSTHETIC FRACTURES ABOUT THE ELBOW

Shawn W. ODriscoll, PhD, MD, and Bernard F. Morrey, MD

As total elbow replacements are being performed more frequently, more periprosthetic fractures are occurring, as with other joint replacements. Although this is a frequent topic of discussion for hips and knees, the literature contains little information to guide treatment of such fractures around the elbow. This article outlines the principles of classification and treatment, based on the authors' clinical experience with more than 1000 total elbow arthroplasties, of which about 80% were primary and 20% revisions. Among the primary procedures, incidence of periprosthetic fractures has been approximately 5%. Although much literature has been written on periprosthetic fractures involving the hip and knee,1-3,5,6,9-'2,14-18 there are no data or published guidelines regarding periprosthetic elbow fractures.

sification applies to both humeral and ulnar fractures. Region

A. Periarticular (Humerus + condyle, epicondyle) (Ulna + olecranon, coronoid)

B. Shaft-around or at tip of stem C. Shaft-beyond tip of stem

1. Well-fixed, adequate bone quality 2. Loose, adequate bone quality 3. Severe bone loss or osteolysis

Status of stem and bone stock

Two additional factors, displacement and tim- ing (intraoperative versus postoperative), are relevant to the treatment of some fractures but not others.

HUMERAL FRACTURES CLASSIFICATION

Based on the authors' clinical experience, it is most useful to consider periprosthetic fractures about the elbow according to the three main factors that determine their prognosis and treatment: the location of the fracture in relation to the stem, the security of the fixation, and the quality of the bone (Fig. 1). These factors are similar to the classification system of Duncan and Masri4 for periprosthetic femoral fractures after total hip replacement. This clas-

Periarticular (Condyle)-Type A

Periarticular (condyle) fractures are the most common type of fracture (Fig. 2) and can occur both intraoperatively and postoperatively. Intraoperative condylar fractures occur as a result of stress applied to the thin bone during positioning of the elbow. This stress can be caused by tension either on the common extensor or flexor tendon origins or on the collateral ligament origins. The latter are

From the Department of Orthopaedic Surgery, Ma yo Clinic, Mayo Foundation, Rochester, Minnesota

ORTHOPEDIC CLINICS OF NORTH AMERICA

VOLUME 30 *NUMBER 2 - APRIL 1999 319

320 ODRISCOLL & MORREY

Figure 1. Periprosthetic fractures of the humerus and ulna can be classified according to the region of the bone involved (A = periarticular; 6 = Shaft: around or at tip of stem; and C = Shaft: beyond tip of stem) as well as the status of the stem and bone stock.

generously released during semiconstrained arthroplasty insertion but retained or at least repaired for resurfacing designs. The bone in the supracondylar region is weakened because of the bony cuts for humeral component insertion. Fractures can also occur at the time of component or trial component insertion if the humeral cuts have been too small or offset me- dially or laterally with reference to the canal.

If the fracture occurs postoperatively, it is usually due to heavy use of the involved mus- culature or a stress fracture from weakened bone as a result of stress shielding or osteolysis. Such fractures are typically treated symptomatically, without surgery, because they rarely remain symptomatic and are ex- tremely difficult to fix successfully. They usually go on to a stable fibrous nonunion, although sometimes they do unite. If the fracture occurs intraoperatively, the surrounding soft tissues are simply sutured together to make possible a stable fibrous nonunion.

Rarely do condylar or epicondylar fractures result in clinically significant pain or functional loss. The bone can be prominent beneath the skin and become irritated. The main con- cern regarding these fractures is that if the prosthesis ever must be removed for infection, the condyles are required to covttain the ulna for a satisfactory resection arthroplasty to be accomp1ished.8 If they are not intact, the elbow remains flail and virtually functionless.

Figure 2. Periarticular (type A) fracture of the lateral humeral column. These can occur at the time of surgery or postoperatively as a fatigue fracture, as in this case. They usually remain minimally displaced and progress toasymp- tomatic nonunions.

PERIPROS1"HETIC FRACTURES ABOUT THE ELBOW 321

Shaft (Around or at Tip of Stem)- Type B

lntraoperative Fractures

If the shaft fractures during surgery, it should be reduced and fixed with cerclage wires, with or without additional onlay allograft struts or plates. If the fracture occurs intraoperatively before stem insertion, it is held reduced, and a stem long enough to bypass and stabilize it is used. If this is not possible or the stem would be unreasonably long, the fracture is plated. Intraoperative fractures are most common during revision procedures, particularly during the removal of a well-fixed infected prosthesis. This risk is also high when revising a humeral stem that is well fixed proximally but with severe osteolysis distally.

Postoperative- Well-Fixed Stem (Type B7)

Fractures in the presence of a well-fixed stem are usually at the tip of the prosthesis. They are treated by open reduction and internal fixation.

Postoperative-Loose Stem (Type 82 and B3)

Humeral shaft fractures around the stem of the prosthesis usually occur in the presence of humeral loosening or osteolysis (Figs. 3-5). If the stem is loose, humeral shaft fractures re- quire revision for two reasons. First, the fracture is not likely to unite. Second, the loose stem remains symptomatic and causes further endosteal erosion. Revision must address the issues of fracture stabilization as well as stem revision. Usually, this revision can be accom- plished by conversion to a long-stem prosthesis, with bone grafting of the fracture site. Ce- ment extrusion must be prevented, not only to permit fracture healing, but also to avoid ther- mal injury to the radial nerve. Revision tech- niques are not the focus of this article, but these can be difficult operation^.^,'^ One must have the skills and tools required for cement removal from a small canal, familiarity with the neural anatomy at all levels of the arm, and the availability of allograft humeral bones and a range of prostheses. Occasionally internal fixation with a plate placed posteriorly along the lateral side of the prosthesis is also neces- sary. An allograft strut can also been used. If osteolysis is severe, impaction bone grafting is

usually performed. Vascularized fibular auto- grafting is an option for failed cases.

Shaft (Beyond Tip of Stem)-Type C

Fractures beyond the tip of the stem are treated as routine humeral shaft fractures with immobilization and functional bracing.

ULNAR FRACTURES

lntraoperative Fractures

As with the humerus, ulnar fractures that occur during surgery should be reduced and fixed with cerclage wires, tension band tech- niques, onlay allograft struts, and plates. An exception would be a fracture of the olecranon in which severe erosion from rheumatoid arthritis had left the bone dangerously thin. In such a case, the bone can be excised and the triceps tendon reattached, or a fibrous union can be achieved using heavy sutures only.

Periarticular (Olecranon) (Type A)

Essentially, periarticular fractures of the ulna involve the olecranon because the coronoid is rarely fractured. The olecranon is prob- ably the second most common fracture involving total elbow arthroplasties. The olecranon is particularly prone to fracture in patients with rheumatoid arthritis because of erosive thinning of the semilunar notch of the ulna (Fig. 6). It is not unusual for there to exist a nonunion of the olecranon preoperatively. Fractures can occur as a result of stress applied to the olecranon during uInar canaI prepara- tion or postoperatively as a result of forceful triceps contraction or a stress fracture. In such cases, the bone is usually thin and unsup- ported by the prosthesis or cement. The long lever arm, combined with the bending mo- ment arm of the triceps, causes fatigue failure of the bone. Also, direct blows or falls on the outstretched arm can cause such fractures.

Treatment is usually determined according to whether or not the olecranon fragment is displaced. If not, a period of immobilization is recommended. This period usually permits a stable fibrous nonunion to develop. If there is significant displacement, the triceps becomes weakened, and open reduction is preferred. If the bone is thin, as is usually the case, it is simply reduced and held with heavy (#5) non-


Figure 3. Periprosthetic humeral shaft fractures are usually associated with loose stems and represent pathological fractures, in the sense that weakened bone (from loosening or osteolysis) is responsible for bone failure. A, Low energy (type 82) fracture at the tip of a loose humeral stem through a region of pathological bone erosion. B, Higher energy comminuted (type 82) periprosthetic fracture extending proximally into the humeral shaft.

absorbable suture through drill holes in the ulna (and into the cement). If the bone fragment is substantial, internal fixation is performed either with tension band wiring or with a plate. One must be prepared, however, to deal with wound complications from the hardware.

Shaft (Around or at Tip of Stem)-

Well- Fixed Stem (Type B 1)

Fractures involving well-fixed stems usually occur right at the tip of the stem. If they are displaced, they are treated by open reduction and internal fixation (see Fig. 6); if they are undisplaced and stable, they are managed by a period of immobilization. One of the authors has incurred two ulnar shaft fractures intraoperatively. The first occurred when the cement hardened prematurely during compo-

Type B

nent insertion, which necessitated hammering the prosthesis into the cement. The second occurred while trying to enlarge the medullary canal in a rheumatoid patient who had significant remodeling of the ulna opposite the bicip- ital tuberosity, with canal encroachment, that had not been recognized on the preoperative radiograph.

Loose Stem (Type B2 and B3)

These fractures usually occur through a por- tion of the ulna that is weakened because of erosion from loosening or osteolysis (Fig. 7). Some of these may present with minimally displaced fractures, but revision is required for two reasons. First, the fracture is not likely to unite. Second, the loose stem remains symptomatic and causes further endosteal erosion, and the fracture is likely to displace. Similar principles as described previously for humeral shaft revisions are employed. Removal of cement from the canal distally is challenging,

PERIPROSTHETIC FRACTURES ABOUT THE ELBOW 323

usually requiring the use of an ultrasonic cement removal device. The primary objective is to bypass the fracture with a longer stem and thereby stabilize it.

Allograft struts, with or without impaction bone grafting, are employed to permit bypass- ing the fracture with a long-stem ulnar component. This component may need to be or- dered as a custom item but is available with at least one semiconstrained prosthesis. Allo- graft-prosthetic composites have been used when the bone is destroyed. If the bone is of adequate quality, it can be fixed by placing a 3.5 DC plate along the posterior surface of the ulna to bridge the fracture site. Screws can be inserted in a unicortical fashion along the side of the prosthesis.

Figure 4. The biomechanics of the elbow would predict that some fractures will occur as a result of the posteriorly di- rected joint resultant force vector. This displaces the humeral stem posteriorly at the distal end and anteriorly at the proximal tip.

Shaft (Beyond Tip Of Stem)-Type

Ulnar fractures beyond the tip of the stem are treated as routine forearm fractures, with

Figure 5. A, Comminuted (type B3) periprosthetic humeral shaft fracture in a region of severe osteolysis and loosening of the humeral stem. 6, This was treated by plate fixation and long-stem revision component with only allograft strut and cerclage wiring.


Figure 6. Ulnar shafl fractures around or at the tip of a well- fixed stem can be treated by internal fixation with a plate and screws, as the bone is wider proximally where the prosthesis is and distal to the tip fixation is possible in nor- mal bone.

Figure 7. Periprosthetic (type 83) ulnar fracture involving the olecranon and the ulnar shaft. Olecranon fractures of- ten occur through thin bone at the isthmus of the olecranon. In this case, there is osteolysis, particularly at the tip of the ulnar stem, where the shaft fractured. Revision is required, but it is difficult.

open reduction and internal fixation mdess minimally displaced.

INDICATIONS FOR SURGERY

General principles govern treatment of fractures about a arthroplasty. They can be summarized according to whether the prosthesis must be revised as part of the treatment or the fracture requires fixation without prosthetic revision. Finally, some cases can be treated nonsurgically as well.

prosthesis and (2) displaced olecranon fracture (open reduction and internal fixation if good bone, suture if thin bone).

NONSURGICAL TREATMENT

Revision The following fractures can be treated non- - surgically:

Revision is indicated for shaft fracture with a loose prosthesis. Undisplaced cracks (unless discovered dur-

ing surgery and easily cerclage wired) Condylar fractures Humeral shaft fractures above the prosthe-

Undisplaced olecranon fractures with intact

Open Reduction and Internal Fixation sis (as with common shaft fractures)

extensor mechanism soft tissues Open reduction and internal fixation is in-

dicated for (1) ulnar shaft fracture with secure

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Address reprint requests to Shawn W. ODriscoll, PhD, MD

Department of Orthopedic Surgery Mayo Clinic

Mayo Foundation 200 First Street SW

Rochester, MN 55905

e-mail: odriscoll.shawn8mayo.edu

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PERIPROSTHETIC FRACTURES ABOUT THE ELBOW