Introduction

Osteochondral fragments can occur in any synovial joint, but they are most commonly encountered in the knee. Typical etiologies include osteochondritis dissecans, trauma (such as the result of patellar dislocation), or nonunion of periarticular fracture.

Osteochondral fragments can also be created by the surgeon in the course of performing osteochondral autografts such as mosaicplasty and mega OATS (Chapters 5 and 6) or osteochondral allografting (Chapter 7).

This chapter reviews the most common methods of fragment fixation.

Indications for Internal Fixation

Few studies provide clear indications for surgical fixation of osteochondral fragments (Table 8-1). The underlying diagnosis has implications in the decision-making process, such as in the treatment of osteochondritis dissecans (OCD).

TABLE 8-1 Indications for Internal Fixation with Regard to Type of Osteochondral Fragment

Type of Osteochondral Fragment	Indication for Fixation
Osteochondral fracture Chondral fracture Osteochondritis Dissecans (OCD)	Fragment is nondeformed, reducible, viable Lesions that are unstable, partially detached lesions, completely detached lesions that are nondisplaced and viable displaced lesions

OCD lesions in situ are much more likely to heal in skeletally immature patients than in adults. Conversely, fragments with lucency on radiographs or fluid on MRI between the fragment and bone bed are less likely to heal and may do better with fixation.

Acute displaced traumatic fragments should be operated in a timely fashion, as there is obviously no opportunity for healing and the fragment risks degeneration as it moves in the joint.

In cartilage repair procedures, the osteochondral graft may require fixation depending on the inherent stability, size, and location of the graft.

To our knowledge, no quantitative measures of graft stability are available to assist the surgeon in deciding when to perform adjunctive fixation.

Juvenile Osteochondritis Dissecans

This diagnosis is classified as an OCD lesion in a patient with open physes demonstrated on radiographic imagery, specifically of the distal femur. The most common patients are athletic, active adolescents.

Surgical indication for juvenile osteochondritis dissecans (jOCD) includes failure of 6 to 9 months of nonoperative treatment of a stable lesion, an unstable or detached lesion, or a symptomatic patient with imminent physeal closure within 6 months to a year.¹

Adult Osteochondritis Dissecans

Unlike jOCD, symptomatic adult OCD necessitates surgical intervention in most cases because of the progressive course, the inability of the fragment to heal on its own, and the fact that most adult lesions are unstable in nature.²

Arthroscopy is useful for determining size and stability of lesions. In situ lesions that are stable during arthroscopic probing can be treated with drilling or internal fixation. Flap lesions (unstable lesions) benefit most from internal fixation techniques.

Massive lesions, multiple fragmented lesions, and substantial craters often require procedures utilizing open bone grafting of the bed or osteochondral autografts and allografts when fixation is not possible or the fragment is not adequate for fixation.³

Traumatic Osteochondral Fragments

The most important decision making in treatment of traumatic osteochondral fragments is whether the fragment has adequate remaining bone to allow both fixation and osseous healing.

In adults there is little evidence that purely chondral fragments have the ability to heal to bone. Nonetheless, surgeons may choose to attempt to repair very thin or small osteochondral fragments with the understanding that there is a significant risk of failure.^4,⁵

One caveat of this approach (and, in fact, in treating any osteochondral fragment with internal fixation) is the avoidance iatrogenic injury to the joint by the fixation device should the fragment collapse or detach, leaving the fixation device proud or loose within the joint. Numerous case reports have documented articular cartilage injury and joint destruction by exposed or loose fixation devices.³^–⁷

Overview of Internal Fixation Devices

The goal of any chosen device should be rigid fixation and compression while establishing a position that is seated low enough as to not interfere with the surrounding articular cartilage (Table 8-2). The device should allow for early range of motion and should retain the ability to be removed, if necessary.⁸

TABLE 8-2 Internal Fixation Devices

Metal Pins and Wires

Smooth and threaded metal pins
K-wires

Cannulated and AO Metal Screws

Constant pitch
Variable pitch, headless (e.g., Herbert screw)

Bioabsorbable Implants

Biocompression screws
Chondral pins and darts (smooth and barbed)

Osteochondral Plugs

Autograft bone plug/Osteochondral core

Pins and Wires

The use of smooth metal pins for fixation was originally described by Smillie in 1957 ⁹ but has since become more of a historical reference. Good results have been published using K-wires in combination with drilling and bone grafting,^8,¹⁰ especially when splitting of a smaller fragment is a concern. Other advantages of K-wires include availability, low cost, and ease of use. Disadvantages include lack of compression achieved and possibility of breakage, along with the need for removal.